Surely the elephant in the room here is Switzerland, where every **** and his dog owns a rifle but few are moved to use them to mow down a bunch of innocent schmoes.
The answer is, clearly, that the problem isn't the guns, it's the mental fúcker pulling the trigger, so as long as these mental septics stick to taking out other septics, the problem is self-resolving. No more septics, no more massacres.