The more you learn the more you realize these people are batshit crazy and reckless.
So apparently, they had a mix of blanks, dummy and LIVE bullets on set, and it isn't uncommon for people to take "prop guns" (what the rest of the world calls "guns") over lunch and go shooting live rounds for target practice!!!
Can you imagine anything so idiotically reckless and dangerous?
Day 1 rule: no live bullets on set.
So many basic, simple, safety rules, each of which would avoid this, all disregarded.
I'm actually amazed now that more people aren't killed regularly in Hollywood. It seems that accidental shootings may happen regularly and as long as no one is killed, no lessons are learned.