trigger happy

/ˈtrɪɡər ˌhæpi/
adjective
  1. Too willing to shoot a gun, often without good reason.
    • The movie showed a trigger-happy cowboy who shot at everything that moved.
    • The police were criticized for being trigger-happy during the protest.
    • A trigger-happy soldier can cause many unnecessary casualties.
  2. Too quick to react or take action, especially in an aggressive or careless way.
    • Some investors are trigger-happy and sell their stocks at the first sign of trouble.
    • The referee was trigger-happy with yellow cards, punishing players for minor fouls.
    • The manager is trigger-happy with firing employees over small mistakes.