noun:a person (especially a man) who uses a gun to shoot someone or to try to shoot someone
noun:a man armed with a gun
synonyms: cain, nimrod, adventurer
Examples
They were shot by an unknown 'gunman'.
Movie quotes
(..) This'll work. Once they divide up, we take them, no trouble, right? Maybe. Boy, for a gunman, you're one hell of a pessimist. They ought to get to where we split up any time. (..)