Since at least 1950, all but two public mass shootings in America have taken place where general citizens are banned from carrying guns. In Europe, there have been no exceptions. Every mass public shooting — and there have been plenty of mass shooting in Europe — has occurred in a gun-free zone. In addition, they have had three of the six worst K–12 school shootings, and Europe experienced by far the worst mass public shooting perpetrated by a single individual (Norway in 2011, which from the shooting alone left 67 people dead and 110 wounded).
The deterrent and life-saving effects of concealed-handgun laws on mass public shootings aren’t just anecdotal. Bill Landes of the University of Chicago and I gathered data on mass public shootings from 1977 to 1999. We studied 13 different types of gun-control laws as well as the impact of law enforcement, but the only law that had a statistically significant impact on mass public shootings was the passage of right-to-carry laws. Right-to-carry laws reduced both the frequency and the severity of mass public shootings; and to the extent to which mass shootings still occurred, they took place in those tiny areas in the states where permitted concealed handguns were not allowed.