It wasn't a prop gun. That's the media's typical framing deception. Prop guns don't have internal mechanisms for firing. Think like karate disarming practice etc. This was a "cold" gun, meaning a real gun that did not have real ammunition in it. But it did. Why would there be a live round on set? Why would the armorer bring a box of live rounds and then say mix in a few into the blanks? It makes no sense at all. Aiming at a camera person? Maybe if they were blocking out a 1st person view of the person being shot, but why not use finger guns? Live ammo, makes no sense. Then he pointed a real gun at someone....not a prop gun. Then he pulled the trigger.