Submachine gun
A submachine gun is a type of gun that shoots many bullets, usually pistol bullets, when one holds down the trigger. A submachine gun is smaller than a machine gun and can easily be carried by one person. They are often used where people need to defend themselves in small areas, or people need to fire many bullets quickly. The first submachine guns were invented in the early 1900s. They are often used by the police and counter-terrorism units .