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.