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A Multi-Level, Multi-Method Investigation of the Psycho-Social Life Histories of Mass Shooters

NCJ Number
Date Published
January 2021
38 pages

This is the Final Report on the goals and achievements of a project that created a database on patterns in the lives of mass shooters to assist in informing policymakers and practitioners in developing and implementing prevention and intervention strategies for mass shootings.


Informed by existing datasets, the research literature, and frequently asked questions about mass shooters, this project compiled a list of variables to be coded and developed a codebook. The codebook was piloted on a small random sample of test cases and refined. Open-source lists of mass shootings were developed from major news outlets. To code the variables of interest, the research team obtained first-person accounts of perpetrators of mass shooters, such as their diaries, “manifestos,” suicide notes, social media and blog posts, audio and video recordings, interview transcripts, and personal correspondence. Secondary sources included existing mass-shooter databases; media coverage; documentary films and podcasts; biographies; monographs and academic journal articles; court transcripts; federal, state, and local law enforcement records; medical records; school records; and autopsy reports. Details are provided on the construction of the database. After officially launching the database to the public in November 2019, “Version 2” of the database was developed based on feedback from users. The database was updated with new mass shootings, and just over 50 new variables. There are now 166 independent variables in the database. Among the variable categories are leakage of the killers’ plans, crisis signs, victim characteristics, firearms possession and use, role of psychosis in the shooting, behaviors related to violence, mental health, family characteristics, and social and interest groups. The report also contains findings from the database on mass shooting trends; shooter demographics; trauma, suicidality, and crisis; mental health; and warning signs. 1 figure, 11 references, and listing of project products

Date Published: January 1, 2021