The presence of a semiautomatic rifle at an active shooter incident increases the number of people who are wounded or killed, according to results published in a research letter in JAMA.

Adil H. Haider, MD, MPH, from the Center for Surgery and Public Health at Brigham and Women’s Hospital in Boston, Massachusetts, and set out to study the rate of injuries and deaths during active shooter incidents based on whether or not a semiautomatic rifle was used.

Dr Haider and colleagues pulled 17 years of data from the Federal Bureau of Investigation (FBI) database of active shooter incidents, which has been tracking incidents since 2000. Researchers extracted shooter demographic information, the number of people wounded, killed, and wounded or killed, the shooting location, and the type of firearm used. Although the FBI database provided the most comprehensive information on each shooting, rifle type was not specified; for those shootings at which a rifle was present, the researchers performed a media content analysis to “identify semiautomatic rifle presence.”

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“Semiautomatic rifles are designed for easy use, can accept large magazines, and fire high-velocity bullets, enabling active shooters to wound and kill more people per incident,” wrote Dr Haider and colleagues.

Nearly 250 (n=248) active shooter incidents were identified by investigators. Of these, 76 involved a rifle, and a semiautomatic rifle was involved in 24.6% of incidents. In total, 898 persons were wounded and 718 were killed. In shooter incidences with a semiautomatic rifle present, there was a higher incidence of persons wounded, killed, and wounded or killed (incidence rate ratio, 1.81, 1.97, and 1.91, respectively).

“Although 44% of persons wounded in active shooter incidents died of their injuries, irrespective of the type of firearm used, more people were wounded and killed in incidents in which semiautomatic rifles were used compared with incidents involving other firearms,” the researchers noted.

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They continued, “Incidents involving semiautomatic rifles may differ from other incidents in ways that may partially explain the association but could not be controlled…. This lack of data highlights the need for a national centralized database to inform the debate on an assault weapons ban.”


de Jager E, Goralnick E, McCarty JC, Hashmi ZG, Jarman MP, Haider AH. Lethality of civilian active shooter incidents with and without semiautomatic rifles in the United States. JAMA. 2018;320(10):1034-1035.