We have knifings in the new on a regular basis. Most people can't make or buy a hand grenade, I think possession illegal according to BATFE. Anyone without a flag can buy an AR-15 variant at a Wal-Mart. A knife won't kill at a hundred yards. A knife won't kill 60 people and wound 500 at a distance of two hundred yards.

What it boils down to is that only weapons like the AR-15 can, under circumstances set up by any sort of person, commit such acts. Murder by truck or car is hard to pull off and not yet "popular". Ammonium nitrate is very hard to obtain, as are all explosives, and generally require a conspiracy of several persons to pull off. Our national mass murder problem is almost exclusively a gun problem. We can't predict who will kill, but we can get the weapons of mass murder off the street.