A Study of Mass Shootings in the United States: The Effects of Mental Health and High Capacity Weapons on Fatalities and Injuries

Abstract

A public mass shooting is defined by federal agencies as a shooting that kills four or more people in a single public location and at a single point in time. This study examined ninety-two cases of public mass shooting in the United States between 1982 and 2018. The study looked to identify common characteristics among mass shootings, specifically looking at the role of assault weapons in public mass shootings, the mental health of the offender, and the connection between state gun laws and public mass shootings. This study found that almost 70% of mass shooters used an assault weapon to carry out their killings, and the use of assault weapons resulted in significantly more fatalities and injuries compared to the use of low-capacity weapons. More than half of mass shooters exhibited signs of mental illness before committing a public mass shooting, and the majority of offenders had a formal record of their mental illness. In addition, this study found that public mass shooting crime rates decreased in states with more lenient gun laws.