It’s the reason you’re taught to treat all firearms as if they are loaded until you’ve confirmed they’re not. It’s easy to lose track of what is and isn’t loade

It’s the reason you’re taught to treat all firearms as if they are loaded until you’ve confirmed they’re not. It’s easy to lose track of what is and isn’t loaded and what it’s loaded with. Doubly so in a chaotic and fast moving environment like a movie set. Then throw in real guns that the person providing has doing double duty and the chances of an accident go right up unless people are careful about their gun handling. Even with defence in depth like you suggest where you properly isolate the guns and keep all live ammo away there still should be no excuse for not properly checking the condition of a weapon before using it. In particular the handling rules are setup so if you accidentally break one or two no one should get hurt. In this case they were deliberately breaking several so only needed to neglect one and tragedy results.