John Lott (of More Guns, Less Crime fame) writes:
Mass shootings occur in places where people of all ages are defenseless, such as so-called gun-free zones in which lots of people congregate and guns are banned. Since at least 1950, all but two of the public shootings in America with more than three deaths have taken place where guns were banned.
Take the Aurora shooting last summer. Within 20 minutes of the murderer’s apartment there were seven movie theaters premiering the Batman movie. The shooter didn’t go to the one that was closest to his apartment. And he didn’t choose the one with the largest audience. Instead, he went to the only one where guns were banned.
I’m not sure these empirical claims would withstand more careful scrutiny (there are likely important confounders here), but certainly this is claim worth more attention that most of the public fussing since Newtown.