The title is clear enough. It tells us that having a pistol there when it matters is the way to go.
Private And Public Law Enforcement In Shooting Attacks
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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 much greater level of deterrence for multiple victim public shootings than for other crimes like murder is consistent with the notion that a higher probability of citizens being able to defend themselves should produce a greater level of deterrence. 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. A particularly surprising result is how the death penalty is so important in deterring murders generally, but has no significant impact on multiple victim public shootings. Finally, the data provides little evidence of either a substitution from shootings to bombings or of "copycat" effects.
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The idea that hanging does not discourage murder is a little surprising. Effective response when it matters is clearly the way to go. As Robert Heinlein said: An armed society is a polite society.