Is that a broomhandle German Luger? BTW who's the idiot that let that guy have the gun?
Probably a shoulder stock. Well seeing that guy's eyes. It may just be a paint broomstick that his buddies told him was a shoulder stock. Forget who give him the gun would you want to be one of the guys around him while he was shooting? On a positive note he can check both directions to make sure everyone is clear before firing, and in doing that he never has to turn his head.