trigger man
From Longman Dictionary of Contemporary Englishtrigger manˈtrigger ˌman noun [countable] American English informal a person who shoots another person, especially when they do this for someone else Even if the trigger men are caught, those who ordered the killing escape punishment.Examples from the Corpustrigger man• He's not just a trigger man.• The way he wrote it, I guessed he was as sure as anyone that I had been the trigger man.