Abstract:
Research Summary: Public mass shootings in the United States have become substantially
more deadly over time. We document this increase, offer a model to explain it, review
supporting evidence for the model, and present new findings on offenders from 1966‐2019. It
appears that societal changes have led to more public mass shooters who are motivated to kill
large numbers of victims for fame or attention, and more shooters who have been directly
influenced by previous attackers. They often spend extended time planning their attacks and
appear increasingly likely to acquire powerful weapons and develop specific strategies to
enhance their lethality.
Policy Implications: New policies should address the aforementioned factors. For instance, the
deadliest public mass shooters’ desires for fame and attention might be countered by a change
in media coverage policies. Additionally, the deadliest perpetrators’ lengthy planning periods
are associated with more warning signs being reported to police, so that information could
justify denying many potential attackers access to firearms through extreme risk protection
orders and red flag laws.
