John Lott's Crime Prevention Research Center notes a number of other instances of armed citizens stopping
would-be criminals. But some of these instances involve off-duty law enforcement officers, who are specially trained for them. Others involve armed citizens stopping knife attacks, and other altercations including armed robberies that you wouldn't normally consider a mass shooting.
On the other hand, the Violence Policy Center has documented
29 mass shootings of three or more people since 2007 where the
perpetrator was himself a concealed carry permit holder. Remember Craig Hicks, the man who allegedly killed three of his neighbors earlier this year in a possible hate crime?
Concealed-carry permit holder. The man who shot up DC's Navy Yard two years ago?
Concealed-carry permit holder. The man who went on a rampage at the American Civic Association in Binghamton, N.Y., in 2009?
Concealed-carry permit holder.
Looks like a concealed carry permit does not a good guy make.