It's said that doves are vicious killers once they get in certain situations, with a confined victim, because they don't have the inhibitions built in that a predator would have, since they aren't equipped with what would normally be dangerous weapons.

I think the same applies with human beings. It's quite hard killing someone with bare hands and teeth (though of course it can be done); but put a gun or a car in our hands, or even a flint knife or a rock, and it's much easier. Too easy.