The FBI study analyzes 154 active shooter events in the U.S. between 2002 and 2012 that included three or more individuals being shot. Conclusions include:

• 96 percent of shooters were males
• 51 percent of shooters were deceased following the attack – 43 percent committed suicide, and 8 percent were shot and killed by responders
• 96 percent of attacks involved shooters acting alone
• 37 percent of the attacks occurred in workplaces; 17 percent occurred in an academic setting
• 40 percent of the attacks were unable to be linked to a clear motivation
• 21 percent of the attacks were motivated by workplace retaliation; 14 percent were motivated by domestic disputes
• Academic retaliation by a current or former student only accounted for 7 percent of attacks

The FBI analysis found that active shooters were often described as “social isolates” who “harbored feelings of hate and anger” and had some contact with mental health professionals, the article says. But while mental illness is a common factor among active shooters, its functional role in the massacres is as of yet undetermined. Very few shooters in the cases analyzed for the study had previous arrests for violent crimes, although many had encountered emotional hardship prior to the attack, such as “loss of significant relationships, changes in financial status, loss of a job, changes in living arrangements, major adverse changes to life circumstances, and/or feelings of humiliation or rejection on the part of the shooter.”

The DHS-FBI joint bulletin recommends that public facilities update their emergency and crisis management plans and conduct exercises to ensure a rapid response to a large-scale crisis. Physical modifications to buildings – such as installing window and external door protections, as well as the establishment of safe areas within facilities – is also recommended.