Gun-free zones and active shootings in the United States: a matched case-control study.

Background: Most Americans believe that gun-free zones make locations more vulnerable to violent crimes, particularly active shootings. However, there is no empirical evidence regarding the impact of gun-free zones on protecting locations from violence. The objective of this study was to estimate the association between gun-free zones and active shootings. Methods: We used a pair-matched case-control study where cases were all US establishments where active shootings occurred between 2014 and 2020, and controls were randomly selected US establishments where active shootings could have but did not occur, pair-matched by establishment type, year, and county. Gun-free status of included establishments was determined via local laws, company policy, news reporting, Google Maps and posted signage, and calling establishments. Findings: Of 150 active shooting cases, 72 (48.0%) were determined to have occurred in a gun-free zone. Of 150 controls where no active shooting occurred, 92 (61.3%) were determined to be gun-free. After accounting for matched pairs, the conditional odds of an active shooting in gun-free establishments were 0.38 times those in non-gun-free establishments, with a 95% confidence interval of 0.19-0.73 (p-value = 0.0038). Several robustness analyses affirmed these findings. Interpretation: It is unlikely that gun-free zones attract active shooters; gun-free zones may be protective against active shootings. This study challenges the proposition of repealing gun-free zones based on safety concerns. Funding: This work was funded in part by the National Collaborative on Gun Violence Research and the Arnold Foundation.