If a person of faith needed to be reminded that killing is a bad thing to do in the first place, religion obviously hasn't stopped them from doing anything. In the scenario you described, anyway, the potential murder was prevented by human interaction and not religion.
Anyway, the quote in my signature is from a song called "Out in the Fields" by Gary Moore and the underlying message is far more literal: bullets don't discriminate. All men are equal when they have a loaded gun pointed at their face.