The gun has to be checked by the people responsible and that includes the one holding it.
Why was he pointing the gun at the camera? Why were two shots fired? Why did the prop people not check and double check this weapon (and it was a weapon).
Thank God he didn't have one of them thar automatic military guns like that AR15 assault rifle. He may have killed the whole crew.
Guns don't kill people. Guns in the hands of untrained idiots kill people.