Mass Murder and Mass Violence: Psychological Evidence and Misconceptions

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Author: Ukrainian Psychological Hub · Published: October 11, 2026 · Editorial Policy

Mass murder and mass violence are extreme forms of harm that invite a deceptively simple question: what kind of person commits such an act? The scientific answer begins with the event being studied. Public mass shootings, killings within families, ideologically motivated attacks, and multiple-victim homicides committed during another crime differ in setting, relationships, available information, and possible motives. No validated universal psychological profile reliably identifies future perpetrators.

Research nevertheless identifies patterns worth examining: previous threats or aggression, developing grievances, changing circumstances, suicidal crises in some cases, preparation, access to lethal means, and opportunities for intervention. Each pattern has a particular evidence base and a particular limitation. A risk factor is an association in a defined population, not a cause of an individual crime; an observed behavior is distinct from a psychiatric diagnosis; a clinical opinion is distinct from the legal finding of responsibility. This article explains what is known about mass murder and mass violence, where evidence remains limited, and how forensic psychology informs prevention without turning retrospective observations into a promise of prediction.

What is mass murder?

Mass murder generally refers to several homicides committed within one incident or closely connected episode. Researchers, police agencies, and lawmakers have applied different casualty thresholds. Some historical FBI descriptions referred to four or more murdered victims. U.S. federal law uses a three-death definition of “mass killing” for a particular federal investigative-assistance purpose. Neither rule creates a universal psychological category or a universally applicable criminal offense. The specific statute and jurisdiction matter.

A mass murder can occur inside a residence, a workplace, a school, a place of worship, or another setting. It may target relatives, acquaintances, people associated with a grievance, or strangers. In some incidents, the perpetrator subsequently dies by suicide or is killed by responders. Counting the attacker among fatalities would change certain statistics, so a sound study explicitly states its rules.

“Mass violence” has a wider operational meaning. It can encompass attacks that cause multiple serious injuries even when a fatality threshold is not met, and it can include methods other than firearms. The U.S. Secret Service National Threat Assessment Center uses an operational framework for mass attacks in public spaces. Its 173 incidents from 2016 through 2020 are a selected sample, not all mass violence or all mass murder.

Mass murder, mass shooting, active shooter, serial murder, and terrorism

A mass shooting involves gunfire and multiple victims under a chosen definition. Certain databases count people shot, including those injured; others require three or four deaths; others focus on public attacks and exclude domestic or crime-related incidents. A mass shooting can therefore appear in one dataset and not another.

An “active shooter” refers to a particular law-enforcement response context: a person actively engaged in killing or attempting to kill in a populated area. Some active-shooter situations result in fewer fatalities than a mass-murder threshold, while some mass murders occur in private without the operational characteristics of an active-shooter event.

Serial murder involves killings separated by time, and its temporal structure warrants distinct forensic analysis. Terrorism can overlap with mass murder, but terrorism involves legal and political classifications of conduct and purpose that vary between jurisdictions. An ideological grievance neither automatically establishes a terrorism charge nor explains every aspect of an offense.

The Congressional Research Service explains the policy consequences of inconsistent mass-shooting definitions. Whenever researchers report a trend or a characteristic of perpetrators, the reader should ask which event category is represented.

Why counts of mass shootings differ so dramatically

Definitions affect findings at a fundamental level. Bridges, Tober, and Brazzell (2023) compared five influential U.S. mass-shooting datasets covering 2013–2020. Together they contained 3,155 distinct incidents, but individual collections ranged from 57 to 2,955 incidents. Only 25 incidents appeared in all five, and substantial differences persisted even under a stricter fatality threshold.

These are differences in inclusion criteria, ascertainment, and documentation, not merely arithmetic mistakes. Including every shooting with multiple people injured produces a different population than selecting attacks in public spaces with several fatalities. Excluding family-related killings changes the distribution of settings and victim–perpetrator relationships. Excluding attacks connected to other felonies changes the motive distribution.

A methodologically responsible analysis discloses geography, period, victim count, injury/fatality rule, perpetrator counting, public/private distinction, and whether domestic and felony-associated incidents qualify. Incident count, number of deaths, number injured, and survivor burden answer separate questions. Any claim that mass violence is increasing or decreasing must name its dataset and time frame.

How psychologists study mass killing

The literature consists largely of observational and retrospective research. Investigators assemble case files, court records, interviews, news archives, communications, medical reports, and structured incident databases. Researchers may code histories of violence, grievances, documented symptoms, relationships, threats, planning, weapons, and outcomes. A 2024 review in the Annual Review of Clinical Psychology synthesizes these multidimensional findings for mass shootings in the United States.

A completed-case study can tell us how frequently a feature appeared among documented attackers. It cannot alone tell us how frequently the same feature occurs among people who never attack. Most features studied—anger, rejection, unemployment, traumatic experiences, suicidal thinking, or social isolation—are much more common than mass murder. That missing comparison population makes individual prediction difficult.

Some findings are strengthened by independent coding and transparent methodology. Others are weakened by sensational reporting, inconsistent records, disputed motives, missing clinical documentation, or hindsight. Researchers must separate facts documented before the offense from interpretations produced after it. The more memorable a case, the greater the temptation to construct a single coherent explanation from information that was fragmented at the time.

Different contexts involve different pathways

Public mass attacks

Some public attackers target a school, business, religious institution, transit location, or other populated area. Their actions may relate to perceived injustice, an interpersonal dispute, ideological motivation, a desire for recognition, or several interacting factors. Selected-case analysis can identify recurring patterns, but it cannot establish a universal sequence that every attacker follows.

The FBI's study of pre-attack behavior in 63 active-shooter cases reported diverse stressors and warning behaviors, while rejecting the idea of a dependable demographic profile. Because that study selected certain incidents and excluded others, its percentages should be reported as features of its own sample.

Domestic and family-related killings

Mass killings within households may arise amid intimate-partner violence, coercive control, separation conflict, threatened loss of relationships, financial distress, and other circumstances. Victims are often known to the perpetrator, which changes the evidentiary relevance of prior abuse, orders of protection, threats, and household dynamics.

Familicide, domestic multiple homicide, and homicide–suicide have overlapping but different definitions. A perpetrator's psychological formulation must distinguish proven events from suggested motives. Characterizing family killings simply as someone “snapping” can obscure a history of decisions, coercion, preparation, or prior harm. Equally, not every domestic tragedy follows the same pathway, and no one family factor is determinative.

Ideologically framed attacks

Ideology can provide a justification for selecting victims, defining enemies, or presenting violence as necessary. Individual resentments and personal crises can coexist with doctrinal statements. The existence of unpopular political or religious ideas is not evidence of intent to commit violence. Investigators need concrete behavior and case-specific corroboration.

Claims about radicalization mechanisms belong to the broader social and political psychology literature; forensic evaluation focuses on the link between documented beliefs, communications, preparation, and criminal acts. Even explicit manifestos require critical reading: an offender may be trying to manipulate audiences or shape the account of the crime.

Killings associated with other crimes

Multiple-victim homicide may also occur during robbery, retaliatory violence, organized criminal disputes, or attempts to conceal another offense. These events have distinct situational incentives, victim-selection patterns, and investigative contexts. Mixing them indiscriminately with public rampage events creates a composite population that may have no single psychological explanation.

Grievance, fixation, anger, and perceived injustice

A grievance is a perceived injury, rejection, threat, or injustice. Grievances occur throughout ordinary life and seldom lead to serious violence. Their forensic significance depends on the behavioral trajectory: what the person did, how statements changed, whether specific targets emerged, and whether preparation or efforts to acquire the means for harm were documented.

Some public attackers describe humiliation, social exclusion, workplace disputes, or revenge. Other motives may include power, dominance, entitlement, ideological hostility, or a wish to acquire notoriety. These are potential components of a case formulation rather than interchangeable clinical diagnoses.

Fixation may describe sustained, escalating attention to a person, event, or grievance. It is most informative when connected to behavioral evidence of escalation, threats, stalking, or preparations. Rumination, anger, or unusual preoccupations alone cannot identify a future offender. Researchers and threat assessors must guard against selecting only the offender's most dramatic post-event quotations to explain a long and complicated history.

Planning, preparation, and the myth of a sudden “snap”

The FBI's selected 63-case active-shooter sample found that 77% of perpetrators had spent at least a week planning an attack, while 46% had spent at least a week preparing the means. These figures come from the FBI's 2018 report. They are important counterexamples to the belief that every mass attack appears with no prior decisions, but they are not rates for all mass murders.

Planning is not itself a single personality variable. Threat evaluators distinguish an angry fantasy from specific intent, an ambiguous statement from a credible threat, and lawful behavior from preparations meaningfully linked to violence. They examine corroborated changes, target choice, escalation, access to means, recent destabilizing events, and available protective circumstances.

There are also attacks with limited known planning or incomplete records. Investigative hindsight can turn disconnected information into an apparently obvious warning sequence. An evidence-based reconstruction states what was actually known, to whom, and when, then identifies intervention opportunities without assuming that an observer could have predicted the eventual outcome.

Is there a mass murderer personality profile?

Research does not support a single validated mass-murderer profile. Labels such as “loner,” “narcissist,” “psychopath,” “bullied youth,” or “social outcast” are common in public commentary and often lack formal assessment, operational definitions, and appropriate comparison groups. A person may display some of these traits and never become violent; an attacker may display none of the popularly expected characteristics.

Psychopathy is a particular psychological construct assessed with specified methods in appropriate contexts. It is not a synonym for severe cruelty, a conclusion that can be drawn from a documentary, or a universal driver of multiple homicide. Personality inventories and risk instruments require attention to reliability, validity, population, setting, and the precise outcome they were developed to assess.

The FBI report explicitly cautions against looking for a single demographic profile. Demographic patterns observed among selected public attackers are descriptive data, not sufficient grounds to screen people in schools, workplaces, or clinical settings. Profiling by identity or broad personality stereotypes generates errors and can undermine fair access to support.

Mental illness, psychosis, and mass murder

A clinical diagnosis describes symptoms and clinical functioning. It does not establish guilt, criminal intent, competence, criminal responsibility, or propensity to commit mass murder. Psychiatric disorders are heterogeneous, and the majority of people with mental illness never engage in serious violence. Several case datasets document some perpetrators with mental health histories, but having symptoms and committing an offense does not prove the symptoms caused it.

In a systematic examination of 172 U.S. public mass shooters based on available records, Peterson and colleagues judged psychosis to have played no role in approximately 69% of cases. Interpretation of possible contributions in other cases involved retrospective material, not a standardized face-to-face examination of all perpetrators. The denominator was a specific group of public mass shooters.

A separate Columbia mass-murder database analysis examined psychotic symptoms across mass killings involving different methods and international settings. Differences between these populations mean their estimates should not be combined as though they described one universal mass-murder phenomenon.

Mental health care is valuable for reducing distress and addressing specific clinical needs. It is only one element of broader violence prevention, which also involves interpersonal relationships, access to means, the response to credible threats, and institutional systems. Stigmatizing people who seek psychiatric help can discourage engagement and obscure more behaviorally relevant information. For the independent clinical evidence, see Schizophrenia and Violence: What Research Really Shows.

Suicide, crisis, and violence directed toward others

Suicidal thinking and self-destructive intent are documented in a subset of mass-attacker research. Some perpetrators die by suicide after an attack or appear to anticipate being killed; others seek escape or survival. These trajectories should not be merged into a single motive. Suicide risk and threat of harm to others are related assessment questions with different outcomes and interventions.

A 2021 JAMA Network Open study of 170 public mass shooters examined communications of intent to harm others before an attack and their associations with mental health and suicide-related variables. Associations must not be read backward as claims that counseling, suicidal thoughts, or depression produce mass murder. Suicidal crises are far more common than multiple-victim homicide.

People communicating distress may need care regardless of any threat-assessment concern. Conversely, credible behavioral evidence of danger to others requires proportionate attention even when no psychiatric disorder has been identified. A dual assessment approach addresses safety and health while preserving clear distinctions between them.

Childhood adversity, stress, and social isolation

Adverse childhood experiences, traumatic losses, interpersonal rejection, financial difficulties, and occupational setbacks appear in some perpetrator histories. These experiences are widespread and lead to many different life outcomes. The idea that childhood trauma creates a direct psychological route to mass killing is not supported by a unique, deterministic mechanism.

The FBI study identified multiple stressors in its selected pre-attack histories, reporting an average of 3.6 stressors within the year before the incidents. This is a completed-case description; it does not establish that a comparable number of stressors predicts who will attack. The timing, meaning, context, and contemporaneous behavior all matter.

Social withdrawal also has multiple meanings: preference for solitude, isolation caused by disability or exclusion, depressed mood, intense engagement in private interests, or a reaction to stress. None is a legitimate proxy for criminality. A robust analysis includes protective relationships, help-seeking, and other competing explanations rather than turning adverse experiences into a narrative of inevitability.

Prior violence, coercive behavior, and threatening conduct

Documented assault, stalking, intimidation, threats, and escalating coercion may be relevant to behavioral assessment because they describe conduct and possible interaction with identifiable people. The Secret Service NTAC's 173 public mass-attack cases included recurring evidence of prior aggressive or concerning behavior. The case definition and retrospective information quality determine how these findings should be used.

Previous aggression is not equivalent to certain future mass violence. Many people who commit ordinary assaults do not commit mass homicide, and some high-profile attackers lack an extensive violent criminal record. A thoughtful evaluation asks whether behavior is recent, escalating, targeted, corroborated, linked to means, or changing in response to interventions.

Investigations also consider whether concern was shared by multiple observers. Family members, colleagues, classmates, or acquaintances may each know different facts. An isolated alarming remark should be understood in context; patterns are more informative when sources and dates are documented.

Gender, social scripts, and cultural context

Many U.S. datasets of public mass shootings contain a large majority of male perpetrators. Researchers therefore examine masculinity norms, dominance narratives, humiliation, status restoration, and gendered scripts for conflict. These are contextual research questions rather than presumptions that being male constitutes a risk designation. The base rate of mass murder among men remains extraordinarily low.

Personal grievances are sometimes articulated through cultural stories about revenge or recognition. Exposure to a cultural script does not determine behavior. Research on class, race, immigration, sexuality, disability, and religion must separate genuine behavioral evidence from unequal surveillance, inconsistent coding, and the differing composition of public and private incident datasets.

The ethical standard is behavioral specificity. A team can document a credible threat, attempts to approach a target, or a pattern of intimidation without equating a protected identity, unusual social presentation, or minority belief with danger.

Online communities, notoriety, and possible imitation

Some perpetrators reference earlier attacks, circulate manifestos, or seek notoriety through media attention. The possibility of imitation or social influence is a legitimate hypothesis and has been examined using incident timing, communication evidence, and statistical models. The size and consistency of an imitation effect remain sensitive to definitions and methods.

Temporal proximity by itself does not prove that one widely reported attack caused another. Similar symbolism, online engagement, or media consumption may have several explanations. If an offender publicly claims inspiration, the claim establishes a recorded statement but requires further corroboration before it becomes a complete causal account.

Journalists and institutions can avoid sensational glorification, minimize unnecessary repetition of perpetrator branding, report verified facts, and emphasize people affected and available support. These practices are ethically reasoned; specific population-level preventive effect sizes require independent evaluation.

Lethal means, environment, and opportunity

Motivation, capability, and opportunity are distinct elements. A grievance does not establish access to weapons; access does not establish intent. The availability and lethality of means can influence the harm produced once a violent act occurs. Settings, emergency response, barriers, and victim vulnerability also matter.

An observational BMJ analysis of U.S. states found associations between firearm ownership proxies, gun-law permissiveness, and mass-shooting incidence. A Law and Human Behavior study assessed associations of state firearm laws with mass-public-shooting incidence and severity over a longer period. These are population-level analyses, sensitive to definitions and confounding; they do not prove that a named law would have prevented one named offense.

The forensic task is to identify situational facts and lawful risk-management options relevant to a particular case. Policy assessment uses different units of analysis and requires separate causal methods.

Can psychologists predict who will commit mass murder?

There is no validated general-purpose test that accurately identifies future mass murderers among ordinary people. Mass murder is rare relative to the enormous prevalence of ordinary distress, anger, grievances, social withdrawal, and even threats. This creates a base-rate problem: a test may seem accurate while producing overwhelmingly more false alarms than correct predictions.

Imagine a hypothetical population of 100,000 people containing one future perpetrator over a stipulated period. A fictional test with sensitivity of 90% and specificity of 99% would flag that one case with 90% probability, yet would also flag about 1,000 people who would not offend. The example uses invented performance values for illustration; it is not a scientific estimate of any available instrument. Reducing false positives usually changes other performance measures and may increase false negatives.

Validity must be assessed for a precisely defined outcome, time window, setting, and population. A tool validated for general violence, institutional incidents, or recidivism is not thereby validated for forecasting mass murder. Calibration, discrimination, false positives, false negatives, subgroup performance, missing data, and the consequences of decisions must be considered. The English Hub analyzes these questions in Violence Risk Assessment: What It Can Predict and Where It Fails.

Threat assessment is a process of managing concerns

Behavioral threat assessment seeks to collect information, understand credible patterns of concern, identify needs and vulnerabilities, and implement proportionate protective interventions. It is a dynamic investigative and management process rather than a diagnostic label or an all-purpose prediction instrument.

The FBI and Secret Service emphasize concrete behavior, multidisciplinary collaboration, information from several sources, and ongoing attention to changes. Relevant questions can concern the credibility of communications, relationships to targets, escalating conflict, preparations, access to means, recent precipitating circumstances, and practical opportunities to interrupt an emerging problem.

The team should document alternative explanations, missing information, the proportionality of interventions, and the person’s access to support. Accurate documentation avoids turning rumor, unusual conduct, or a protected viewpoint into proof. For a detailed account of offender-focused threat pathways, see Lone-Actor Violence and Threat Assessment: Risk Factors and Limits.

What is “leakage” in mass violence research?

“Leakage” refers to communication of an intention to harm before the incident. Communications might be direct threats, indirect statements, written messages, online posts, or conversations. Its coding depends on the study's definition and available evidence. Leakage is a research category for observed behavior, not a psychiatric diagnosis or an automatic finding of imminent danger.

Peterson and colleagues (2021) reported communication of intent among 46.5% of the 170 public mass shooters in their selected sample. This is the prevalence of a coded feature among people who completed the offense. It is not the probability that someone who makes a concerning statement will attack.

The interpretive questions concern specificity, source, timing, context, corroboration, target, associated preparations, and evolving behavior. Responsible reporting channels allow concerns to reach trained staff while discouraging the assumption that ordinary expressions of frustration or symptoms of a disorder automatically reveal criminal intent.

Psychological explanation versus legal responsibility

Psychology and law ask different questions. A grievance is an inferred psychological construct. A recorded statement or action is behavioral evidence. A risk factor is a statistical association. A clinical diagnosis concerns diagnostic criteria and functional impairment. A psychometric score summarizes instrument responses under a specified model. A forensic opinion addresses a psycholegal referral question while explaining methods and limitations.

Legal guilt, criminal intent, competency to stand trial, criminal responsibility, admissibility of evidence, and an insanity defense are governed by law. Standards differ between U.S. jurisdictions and across national systems. Expert testimony may inform a legal decision, but the presence of a mental disorder or risk score cannot itself prove an offense or supply the applicable legal test.

Investigators should separate facts known before an event, contemporaneous clinical findings, later retrospective assessments, prosecutorial allegations, judicial decisions, and speculation. When a suspected perpetrator dies, the absence of a complete adversarial process can increase uncertainty about motives and psychiatric history. Extreme violence does not justify assigning a diagnosis to someone who was never clinically assessed.

What the research cannot tell us

Selected samples and missing denominators

Case databases often contain only people who completed attacks. They tell us the prevalence of particular features among known cases, not the frequency of those features in a comparable non-offending population. Without a comparison group, the apparent importance of a characteristic can be exaggerated.

Incomplete records and retrospective interpretation

Clinical histories may be unavailable, motives disputed, and pre-event behavior ambiguously recalled. Well-known incidents attract more documentation, introducing reporting bias. The narrative clarity of an investigation conducted after an attack differs from the information available to a school, clinician, colleague, or family member before it.

Small event counts and category instability

Narrow definitions of fatal public mass shootings often yield relatively few events, so the addition of a small number of cases can materially alter percentages. A study's temporal window, inclusion rules, ascertainment process, and statistical uncertainty belong alongside its conclusions.

Correlation, causation, and external validity

A statistical link between a characteristic and completed offenses is not proof that the characteristic caused an individual crime. Risk factors can be influenced by socioeconomic context, environmental exposures, access to means, prior interventions, and selection effects. Findings from one country or type of attack may not transfer to domestic killings, extremist bombings, or juvenile violence elsewhere.

Fairness and calibration

A measure that performs tolerably in one research population may misclassify people in another. Group differences in detection, reporting, culture, or institutional responses can also affect recorded outcomes. These problems are particularly serious where a decision could restrict freedom, education, employment, or treatment.

Prevention: promising practices and evidence limits

A credible prevention strategy combines behavioral concern reporting, professional assessment, timely case management, support for people in crisis, attention to prior violent conduct, and measures that reduce immediate opportunities for harm when justified. The appropriate balance changes with context, law, individual needs, and the available facts.

Retrospective attack studies show that some completed cases had observable concerns and opportunities for intervention. That is an important rationale for assessing threatening behavior. It does not by itself quantify how many future mass killings will be prevented by a specific threat-assessment program. Measuring prevention is difficult when outcomes are rare and many possible attacks remain unobservable counterfactuals.

Broader studies of domestic-violence prevention, firearms safety, suicide prevention, school climate, and community intervention can inform public-safety decisions, but an effect demonstrated for a broad violence outcome should not be presented as a proven mass-murder-specific effect. Evaluation should monitor not only attacks but also referrals, supportive interventions, false alarms, rights violations, and institutional learning.

Practical response in schools, workplaces, and communities

The most useful first action is to document specific behavior and bring credible concerns to a qualified local reporting channel. A factual report identifies who observed what, when it occurred, the exact communication or behavior, the source of the information, any identifiable target, and corroborating evidence. It separates firsthand knowledge from hearsay and records subsequent changes.

Institutions benefit from clearly defined multidisciplinary responsibilities, proportionate escalation pathways, lawful information sharing, crisis supports, and procedures for reviewing decisions. Students, employees, and patients should not be labeled dangerous because of diagnosis, disability, isolation, unpopular views, or appearance.

For an immediate credible threat of violence, follow local emergency procedures and contact emergency services. A bystander can report factual concerns without attempting to diagnose anyone or independently investigate dangerous conduct.

Ethics, privacy, and cultural fairness

Protecting potential victims and protecting civil liberties are simultaneous duties. False positives can seriously affect families, livelihoods, educational trajectories, treatment access, and community trust. Systems must distinguish observation from interpretation and document why a particular intervention is justified.

Cultural and language differences affect the meaning of reported statements. Neurodivergent communication, social anxiety, atypical behavior, minority beliefs, and symptoms of mental illness do not establish violence risk. Fair decisions rely on corroborated conduct, context, relevant expertise, and transparent review rather than demographic or diagnostic stereotypes.

Sensitive information requires appropriate confidentiality safeguards and jurisdiction-specific legal authority for sharing. Expert claims should describe the strength of the underlying research, uncertainty in individual application, and the practical consequences of potential error.

Common misconceptions

Myth: every mass murderer was severely mentally ill

The available studies identify heterogeneous histories and motives. Psychotic symptoms may contribute in certain cases, but diagnosis and causation are separate questions, and the majority of the affected clinical population is not involved in violent offending.

Myth: investigators can recognize the future attacker by personality

No universal validated mass-murderer personality test exists. Broad labels and demographic likenesses provide poor discrimination for an extremely rare event. Behavioral facts and context are more informative than stereotypes.

Myth: mass murder always happens without warning

Some studied attacks involved prolonged planning, preparation, and observable concern. Others have incomplete histories or different trajectories. Pre-event signs are neither universal nor certain predictions.

Myth: anyone who communicates violence will carry it out

Threats and concerning statements vary in intent, specificity, credibility, and context. The great majority of people with a concerning indicator will not commit mass murder. Assessment aims to clarify and manage concern, not to presume guilt.

Myth: a risk score proves future mass homicide or criminal responsibility

A score is an assessment output for a specified instrument and outcome. Its interpretation depends on validation, population, calibration, error rates, and the decision context. It is not a verdict or proof of intent.

Myth: statistics about public shootings describe every mass killing

Definitions often exclude domestic incidents, other weapons, or crimes arising from other offenses. Each population warrants a separate account before claims are generalized.

Frequently asked questions

What is the difference between mass murder and mass shooting?

Mass murder generally concerns multiple deaths within one incident. Mass shooting concerns firearm violence and may include multiple people injured without requiring deaths. The threshold and inclusion rules depend on the source.

Is mass murder a mental disorder?

No. It is a category of violent event or offense, not a psychiatric diagnosis. Psychological research can examine circumstances and behavior without equating criminal acts with diagnostic criteria.

Why do people commit mass murders?

There is no single cause or motive. Different cases involve interpersonal grievances, domestic conflict, ideology, retaliation, notoriety, other criminal objectives, crises, access to means, and changing situational factors. Motive determination requires evidence specific to the event.

Are mass murderers usually psychotic?

Research on selected public mass shooters found psychosis was not considered a meaningful contributor in most examined cases. The rates depend on sample and retrospective record quality. The presence of psychosis among some offenders cannot be generalized into a prediction about patients.

Does bullying or childhood trauma cause mass murder?

Such experiences occur in some offender biographies and in many people who never become violent. A personal history of adversity is neither a unique cause nor a reliable screening rule.

Are most mass murderers men?

Men are the large majority in several U.S. public-shooting samples. That descriptive demographic pattern has negligible individual screening value because mass murder is extraordinarily rare.

Can mass violence be prevented?

Some cases contain observable behavioral escalation, threats, preparation, or crises that provide opportunities for intervention. Prevention systems can respond to specific concerns, but no intervention or assessment guarantees that every event will be averted.

Does online content cause mass killing?

Certain attackers reference prior incidents or circulate violent narratives. Causal effects of media exposure or online participation require stronger evidence than similarity or timing, and conclusions depend on individual and population-level research.

Is mass murder the same as terrorism?

They can overlap. Mass murder concerns multiple homicide victims under a definition; terrorism concerns legally and politically defined purposes and conduct. Jurisdiction and case facts determine the legal designation.

Are mass shootings becoming more common?

A trend requires a named dataset, definition, location, observation period, and denominator. Broader and narrower databases do not count the same incidents and may support different trend descriptions.

What is the difference between profiling and threat assessment?

Profiling attempts to infer offender characteristics or identify a type from crime features. Behavioral threat assessment investigates a specific evolving concern, evaluates available behavior, and guides interventions. Neither process establishes guilt or certain future behavior.

Where does this article fit within forensic psychology?

This article focuses on the multiple-victim offense category and the strength of the explanatory evidence. General criminal behavior, violence risk, and lone-actor threat assessment are separately developed forensic topics.

Conclusion

Mass murder and mass violence cover different behaviors, victims, settings, and motives. Research can describe recurrent features of selected attack populations and inform a fair response to concrete threats. The strength of a scientific explanation lies in retaining precise definitions, distinguishing verified behavior from inferred motivation, and recognizing the rarity that makes individual prediction inherently error-prone.

The most defensible approach uses documented conduct, corroboration, awareness of changing circumstances, professional judgment, appropriate clinical support, and lawful proportionate intervention. The evidentiary limits of every instrument, diagnosis, and retrospective theory remain part of that work.

References

Bridges, T., Tober, T. L., & Brazzell, M. (2023). Database discrepancies in understanding the burden of mass shootings in the United States, 2013–2020. The Lancet Regional Health – Americas, 22, 100504. https://doi.org/10.1016/j.lana.2023.100504.

Brucato, G., et al. (2022). Psychotic symptoms in mass shootings versus mass murders not involving firearms: Findings from the Columbia mass murder database. Psychological Medicine. https://doi.org/10.1017/S0033291721000076.

Congressional Research Service. (2024). How to Define Mass Shootings: Potential Policy Implications. Report R48276. Official congressional report.

Peterson, J. K., Densley, J. A., Hauf, M., & Moldenhauer, J. (2024). Epidemiology of mass shootings in the United States. Annual Review of Clinical Psychology, 20, 125–148. https://doi.org/10.1146/annurev-clinpsy-081122-010256.

Peterson, J. K., Densley, J. A., Knapp, K., Higgins, S., & Jensen, A. (2022). Psychosis and mass shootings: A systematic examination using publicly available data. Psychology, Public Policy, and Law. https://doi.org/10.1037/law0000314.

Peterson, J., Erickson, G., Knapp, K., & Densley, J. (2021). Communication of intent to do harm preceding mass public shootings in the United States, 1966 to 2019. JAMA Network Open, 4, e2133073. https://doi.org/10.1001/jamanetworkopen.2021.33073.

Reeping, P. M., Cerdá, M., Kalesan, B., Wiebe, D. J., Galea, S., & Branas, C. C. (2019). State gun laws, gun ownership, and mass shootings in the US: Cross-sectional time series. BMJ, 364, l542. https://doi.org/10.1136/bmj.l542.

Siegel, M., Goder-Reiser, M., Duwe, G., Rocque, M., Fox, J. A., & Fridel, E. E. (2020). The relation between state gun laws and the incidence and severity of mass public shootings in the United States, 1976–2018. Law and Human Behavior. https://doi.org/10.1037/lhb0000378.

Silver, J., Simons, A., & Craun, S. (2018). A study of the pre-attack behaviors of active shooters in the United States between 2000 and 2013. Federal Bureau of Investigation. Official FBI report.

U.S. Secret Service, National Threat Assessment Center. (2023). Mass attacks in public spaces: 2016–2020. Official federal report.

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