"You shall cut off her hand; you shall not pity her"Deuteronomy 25:12.

We are commanded to save a potential victim from the hands of one who is "chasing" him to kill him—even if this means killing the attacker. If it is possible to save the victim without killing the pursuer – through injuring the attacker, then that must be done. But if that is not possible, we are commanded to kill the pursuer rather than allow him to execute his dastardly intention.