With 350,000,000ish people in the U.S. odds are there will always be a few crazies, mentally deformed or outright idiots. Look at the possibilities, if .000001% fell into that category, there would be 350 killers.
If you took away all the guns, knifes, bullets, gun powder, arrows, sling shots, poisons, cars, trucks, clubs or whatever, they would steal whatever they could to kill. If we ban baseball bats, forks, rocks, bottles, chainsaws and take all weapons away from the police and military, they would still kill, maybe with their bare hands.