That's a strawman. Even if that weren't true, the link is trivial to anyone honest about this and not "defensive" about violent games.
Another example is guns. True guns don't kill people, but put them in the wrong hands and it makes for some silly situations.
@Somini, just read your reply. Funny how I mentioned guns in my reply to hsrob :)
It would only be a strawman if I was genuinely claiming that is the position put forth which of course I wasn't ;)
It troubles me though that games are being looked at as a cause by the police when logic dictates that even if they are 'proven' to be part of the problem here they are clearly not the main issue. Games are ubiquitous in the developed world, mass shootings and school shootings are not.
Trying to finger games seems at best to be oversimplifying an issue that simply isn't simply, and at worst, blatent scapegoating.
Neither approach can possibly lead to a solution that will decrease the number of innocent people being killed by gun (or any other kind of) violence. I have no prejudice in how that solution is arrived at, if it takes more guns, so be it. However, trying to prove a link, after-the-fact, if that is one's intention, will inevitably lead to proof in the positive but not necessarily the correct conclusion.