Armed Citizens and Multiple Victim Shootings

Here is a link to "Multiple Victim Public Shootings, Bombings, and Right-to-Carry Concealed Handgun Laws: Contrasting Private and Public Law Enforcement".

The authors are John Lott (Crime Prevention Research Center) and William Landes (University of Chicago Law School, National Bureau of Economic Research).

Lott and Landes are preeminent researchers in the field.  In contrast, their critics' work has been shown to be flawed statistically and/or logically.

The abstract reads:

Few events obtain the same instant worldwide news coverage as multiple victim public shootings. These crimes allow us to study the alternative methods used to kill a large number of people (e.g., shootings versus bombings), marginal deterrence and the severity of the crime, substitutability of penalties, private versus public methods of deterrence and incapacitation, and whether attacks produce copycats. Yet, economists have not studied this phenomenon. Our results are surprising and dramatic. While arrest or conviction rates and the death penalty reduce normal murder rates, our results find that the only policy factor to influence multiple victim public shootings is the passage of concealed handgun laws. We explain why public shootings are more sensitive than other violent crimes to concealed handguns, why the laws reduce both the number of shootings as well as their severity, and why other penalties like executions have differential deterrent effects depending upon the type of murder.

The conclusion reads:

The results of this paper support the hypothesis that concealed
handgun or shall issue laws reduce the number of multiple victim
public shootings. Attackers are deterred and the number of people
injured or killed per attack is also reduced, thus for the first time
providing evidence that the harm from crimes that still occur can be
mitigated. The results are robust with respect to different
specifications of the dependent variable, different specifications of
the handgun law variable, and the inclusion of additional law
variables (e.g., mandatory waiting periods and enhanced penalties for
using a gun in the commission of a crime). Not only does the
passage of a shall issue law have a significant impact on multiple
shootings but it is the only law related variable that appears to have a
significant impact. Other law enforcement efforts from the arrest
rate for murder to the death penalty to waiting periods and
background checks are not systematically related to multiple shootings.
We also find that shall issue laws deter both the number
of multiple shootings and the amount of harm per shooting. Finally,
because the presence of citizens with concealed handguns may be
able to stop attacks before the police are able to arrive, our data also
allows us to provide the first evidence on the reduction in severity of
those crimes that still take place.