Preventing mass shootings in the United States, particularly those occurring in school settings, is an important priority for families, government leaders and officials, public safety agencies, mental health professionals, educators, and local communities. What does the evidence say about how to detect, prevent, and respond to these tragic events? Here’s what we’ve learned through NIJ-sponsored research:
1. Most people who commit a mass shooting are in crisis leading up to it and are likely to leak their plans to others, presenting opportunities for intervention.
Before their acts of violence, most individuals who carry out a K-12 mass shooting show outward signs of crisis. Through social media and other means, they often publicly broadcast a high degree of personal instability and an inability to cope in their current mental state. Almost all are actively suicidal.
Case studies show that most of these individuals engage in warning behaviors, usually leaking their plans directly to peers or through social media. Yet most leaks of K-12 mass shooting plans are not reported to authorities before the shooting.
Research shows that leaking mass shooting plans is associated with a cry for help. Analyses of case reports from successfully averted K-12 mass shootings point to crisis intervention as a promising strategy for K-12 mass shooting prevention. Programs and strategies found to prevent school shootings and school violence generally could hold promise for preventing school mass shootings as well.
2. Everyone can help prevent school mass shootings.
Most individuals who carry out a K-12 mass shooting are insiders, with some connection to the school they target. Often, they are current or former students.
Research suggests that communities can help prevent school mass shootings by working together to address student crises and trauma, recognizing and reporting threats of violence, and following up consistently.
Two-thirds of foiled plots in all mass shootings (including school mass shootings) are detected through public reporting. Having a mechanism in place to collect information on threats of possible school violence and thwarted attempts is a good first step.
The School Safety Tip Line Toolkit is one resource to consider for developing and implementing a school tip line. The Mass Attacks Defense Toolkit details evidence-based suggestions for recognizing warning signs and creating collaborative systems to follow up consistently in each case. The Averted School Violence Database enables schools to share details about averted school violence incidents and lessons learned that can prevent future acts of violence.
3. Threat assessment is a promising prevention strategy to assess and respond to mass shooting threats, as well as other threats of violence by students.
For schools that adopt threat assessment protocols, school communities are educated to assess threats of violence reported to them. Threat assessment teams, including school officials, mental health personnel, and law enforcement, respond to each threat as warranted by the circumstances. An appropriate response might include referral of a student to mental health professionals, involvement of law enforcement, or both.
Emphasizing the mental health needs of students who pose threats can encourage their student peers to report on those threats without fear of being stigmatized as a “snitch.” In an evaluation study, educating students on this distinction increased their willingness to report threats.
Many educational and public safety experts agree that threat assessment can be a valuable tool. But an ongoing challenge for schools is to implement threat assessment in a manner that minimizes unintended negative consequences.
4. Individuals who commit a school shooting are most likely to obtain a weapon by theft from a family member, indicating a need for more secure firearm storage practices.
In an open-source database study, 80% of individuals who carried out a K-12 mass shooting stole the firearm used in the shooting from a family member. In contrast, those who committed mass shootings outside of schools often purchased guns lawfully (77%).
K-12 mass shootings were more likely to involve the use of a semi-automatic assault weapon than mass shootings in other settings, but handguns were still the most common weapon used in K-12 mass shootings.
Explore more information about the backgrounds, guns, and motivations of individuals who commit mass shootings using The Violence Project interactive database.
5. The overwhelming majority of individuals who commit K-12 mass shootings struggle with various aspects of mental well-being.
Nearly all individuals who carried out a K-12 mass shooting (92%-100%) were found to be suicidal before or during the shooting. Most experienced significant childhood hardship or trauma. Those who commit K-12 mass shootings commonly have histories of antisocial behavior and, in a minority of cases, various forms of psychoses.
Despite the prevalence of mental well-being struggles in these individuals’ life histories, studies suggest that profiling based on mental health does not aid prevention.14 However, research on common psychological factors associated with K-12 mass shootings, along with other factors that precipitate school violence, can help inform targeted intervention in coordination with crisis intervention, threat assessment, and improved firearm safety practices.
Learn more from these NIJ reports:
- Understanding the Causes of School Violence Using Open Source Data
- A Multi-Level, Multi-Method Investigation of the Psycho-Social Life Histories of Mass Shooters
- The Causes and Consequences of School Violence: A Review
- A Comprehensive School Safety Framework: Report to the Committees on Appropriations
[note 1] National Institute of Justice funding award description, “Student Threat Assessment as a Safe and Supportive Prevention Strategy,” at the Rector & Visitors of the University of Virginia, award number 2014-CK-BX-0004; National Institute of Justice funding award description, “Understanding the Causes of School Violence Using Open Source Data,” at the Research Foundation of the City University of New York, award number 2016-CK-BX-0013; National Institute of Justice funding award description, “Mass Shooter Database,” at Hamline University, award number 2018-75-CX-0023, and National Institute of Justice funding award description, “Improving the Understanding of Mass Shooting Plots,” at the RAND Corporation, award number 2019-R2-CX-0003.
[note 2] Meagan N. Abel, Steven Chermak, and Joshua D. Freilich, “Pre-Attack Warning Behaviors of 20 Adolescent School Shooters: A Case Study Analysis,” Crime & Delinquency 68 no. 5 (2022): 786-813.
[note 3] Jillian Peterson et al., “Communication of Intent To Do Harm Preceding Mass Public Shootings in the United States, 1966 to 2019,” JAMA Network Open 4 no. 11 (2021): e2133073.
[note 4] Abel, Chermak, and Freilich, “Pre-Attack Warning Behaviors”; and Jillian Peterson and James Densley, The Violence Project: How To Stop a Mass Shooting Epidemic (New York: Abrams Press, 2021).
[note 6] RAND Corporation, “Mass Attacks Defense Toolkit: Preventing Mass Attacks, Saving Lives."
[note 7] National Police Foundation, Averted School Violence (ASV) Database: 2021 Analysis Update, Washington, DC: U.S. Department of Justice, Office of Community Oriented Policing Services.
[note 8] Dewey Cornell and Jennifer Maeng, “Student Threat Assessment as a Safe and Supportive Prevention Strategy, Final Technical Report,” Final report to the National Institute of Justice, award number 2014-CK-BX-0004, August 2020, NCJ 255102.
[note 9] Shelby L. Stohlman and Dewey G. Cornell, “An Online Educational Program To Increase Student Understanding of Threat Assessment,” Journal of School Heath 89 no. 11 (2019): 899-906.
[note 10] Cornell and Maeng, “Student Threat Assessment.”
[note 11] Jillian Peterson, “A Multi-Level, Multi-Method Investigation of the Psycho-Social Life Histories of Mass Shooters,” Final report to the National Institute of Justice, award number 2018-75-CX-0023, September 2021, NCJ 302101.
[note 13] Peterson, “A Multi-Level, Multi-Method Investigation.” 14Dewey G. Cornell, “Threat Assessment as a School Violence Prevention Strategy,” Criminology & Public Policy 19 no. 1 (2020): 235-252.