From the articleThe death of director of photography Halyna Hutchins on a film set in Santa Fe, N.M., is a reminder that prop weapons can pose a serious risk. But Hollywood history includes only a few such incidents.www.npr.org
"In addition to safety lessons and practice sessions, actors are told to keep a safe distance from other crew members when handling a prop gun. Filmmakers often use movie magic so it looks as if an actor is pointing a gun directly at another character — when they're actually pointing the weapon at an angle or off-center."
They expect us to believe that actors are trained not to even point their fake guns at people on camera, but Alec somehow slipped and close-range blasted someone who was by definition off camera, and that unlucky blast from a fake gun was fatal.