In 2017, Densley and psychologist
Jillian Peterson of
Hamline University co-founded The Violence Project. Their first initiative, in partnership with the Minnetonka Police Department, was the development of a mental illness crisis intervention training for law enforcement known as the R-Model. With funding from the
National Institute of Justice, Densley and Peterson created a database of all public mass shooters since 1966 coded on more than 150 life history variables. Their research has examined K-12 school shootings and the influence of the
Columbine High School massacre as a model for subsequent attacks. Densley and Peterson have also criticized active shooter drills in schools, arguing that such exercises can traumatize children and normalize violence. In a
viral 2019 op-ed for the
Los Angeles Times, Densley and Peterson outlined a framework for understanding
mass shootings. Drawing on interviews with perpetrators and their acquaintances, they identified four recurring themes: early childhood trauma, a crisis point involving suicidality, validation through the study of prior shootings, and access to firearms. They argue that addressing each factor—through firearm regulation, suicide prevention, social support, and limiting media contagion—can help prevent future attacks. This framework is expanded in their book,
The Violence Project: How To Stop a Mass Shooting Epidemic, Their research has also emphasized that many mass shooters "leak" their intent beforehand as a cry for help, suggesting opportunities for early intervention. The Violence Project continues to maintain open-source databases tracking mass public shootings, as well as homicides in schools, places of worship, college campuses, workplaces, and attacks on elected officials. Analyses of these data, including a
Bloomberg report following the 2025 killing of conservative activist
Charlie Kirk, have been used to highlight trends in political violence in the United States. == Growing Against Violence ==