Imagine a commando in World War II who is dropped behind enemy lines posing as a German officer so he can get into a concentration camp and destroy the gas chambers. Imagine next that as he mingles with other officers he sees a soldier preparing to execute a prisoner. This is an evil he could stop by simply shooting the soldier, but at what cost? He might save one person, but his mission is to save many. More lives would be lost in the long run if he prevents an individual death, but does not stop the gas chambers from destroying thousands.
