JMIR Publications

ABSTRACT

Background:

Public mass shootings are a significant public health problem that require systematic surveillance to inform policies that combat gun injuries. While there is widespread agreement that something needs to be done to stop public mass shootings, exactly which policies that entails varies such as the prohibition of assault weapons and large capacity magazines.

Objective:

The objective of this is study is to explore the relationship between the concurrent FWAB/LCMB and public mass shooting events from 1966 through 2019. This study differs significantly from earlier studies in time period covered, methods –and most notably, the primary outcome being the number of public mass shooting and number of fatalities and injuries vs. overall firearm homicides.

Methods:

We extracted public mass shooting surveillance data from the Mother Jones Mass Shooting and the Violence Project surveillance systems that matched our inclusion criteria of four or more fatalities in a public space during a single event. We performed regression discontinuity analysis, taking advantage of the imposition of the FAWB which includes a prohibition on large capacity magazines (LCM) in addition to assault weapons. We estimated a regression model of the five-year moving average number of public mass shootings per year for the period 1970 to 2018 controlling for population growth and homicides in general; introduced regression discontinuities in the intercept and a time trend, for years coincident with the federal legislation i.e. 1995-2004, and also allowed for a differential effect of the homicide rate during this period. We introduced a second set of trend and intercept discontinuities for post-FAWB years to capture the effects of the termination of the policy. We use regression results to predict what would have happened from 1995 to 2019 had there been no FAWB and also to project what would have happened from 2005 onward had it remained in place.

Results:

The FAWB resulted in a significant decrease in public mass shootings, number of gun deaths and injuries. We estimate the FAWB prevented 11 public mass shootings during the decade the ban was in place. A continuation of the FAWB would have prevented 30 public mass shootings that killed 339 people and injured an additional 1139 people.

Conclusions:

This study demonstrates the utility of public health surveillance on gun violence. Surveillance informs policy on whether a ban on assault weapons and high capacity magazines reduces public mass shootings. As society searches for effective policies to prevent the next public mass shooter, we must consider the overwhelming evidence that assault weapon bans and/or large capacity magazine bans work. Clinical Trial: NA