Maybe a better answer is that we need to treat our crazy people. It's not a matter of expense; either you pay money to treat mental illness, or you pay money to clean up after them. I'd rather spend on getting them help than in burying our children.

I can go into a store today and buy everything needed to blow a building to bits. Remember Oklahoma City? If you don't want a big boom, you can always go the bleach and ammonia route. If you want to kill or maim people in mass quantities, you don't need a gun. You can use a car. Or a plane. I suppose banning planes is next?