I think you're missing the point. Does the gun matter? If guns didn't exist, would the person who committed these crimes (or about to go) "welp, I really would prefer to kill that guy with a different method, but since I can't, I'll just forget it."
Ah, gotcha.
Yes they would use knifes, clubs, whatever it took to still kill each other.
Crime equal federal money, the city loves it.