John R. Lott, Jr. is an expert on this topic:
Has anyone noticed that these mass shootings at public schools increased after the 1995 Gun-Free School Zone Act? Passed with good intentions, banning guns would supposedly make schools safer.
But law abiding citizens, not criminals, obey these bans. Instead of making places safer, disarming law abiding citizens left them sitting ducks.
Killers go where victims can’t defend themselves. In the Aurora, Colo., movie theater shooting, out of seven theaters showing the Batman movie premiere within 20 minutes of the suspect’s apartment, only one banned permitted concealed handguns. The suspect didn’t go to the closest nor the largest, but to the one that banned self-defense. Time after time the story is the same.