The difference between what happened with Brandon Lee and what happened with Halyna Hutchins was that with Brandon Lee, the production was at fault for sending the firearms expert home early because there was only one more gunshot to go, and the props assistant could handle it for the final two weeks of shooting. But it was more a cumulative chain of errors, and no one knew better.
For example, they made dummy cartridges for a close-up shot by dumping out the powder and crimping the bullet back into an empty case. Because the expert was gone, no one told them the primer still has enough energy to push a bullet an inch or two into the barrel. Someone pulled the trigger thinking they were harmless, and didn't notice that faint 'click' of what all of us know in the firearms business is a primer pop. One week later, they loaded it with a blank but there was no one there to CHECK THE BARREL, and no one there to tell the actor Michael Massee to aim slightly to the side. The production was negligent by sending the expert home early, but it was a long chain of errors. If they had learned the PROVE procedure, he would still be alive today.
PROVE saves lives.
In the situation of the "Rust" shooting, they knew full well what they were doing and they deliberately broke all the rules and procedures in place that would have saved her life.
The armorer brought live ammunition to set because she loved to show off her quick-draw prowess to the crew. She was also extremely inexperienced. Live ammunition is NEVER allowed on a film set, plus there are hundreds of safety checks and safety steps done every done on every gun to make sure this never happens. They skipped all those.
The First AD grabbed a gun off the table - which is not his job, and is NEVER done on a film set - and handed it to the actor without checking. He told the actor it was a "cold" gun, meaning empty of all blanks.
The actor Alec Baldwin was lining up a shot toward the camera in a rehearsal. For some reason he pulled the trigger thinking it was empty. He probably cocked the hammer to rehearse his draw from the holster and thinking it was empty, pulled the trigger.
While the actor was not directly at fault here, it should be noted that as a producer, HE (along with the other producers) made the decision to hire someone inexperienced and cheap. HE was the one who hadn't paid his crew in 7 weeks. HE was the one who refused accommodation, and when they insisted, HE was the one who put them up in some dirty hooker motel and forced them to sleep in their cars instead. HE was the one who refused to respond to complaint after complaint after complaint about abusive hours and unsafe gun handling practices on set.
The morning of the incident, his entire union camera crew walked off the job, citing hours and safety. HE was the one who replaced them with local non-union hires and local film students.
The big difference here is that three people were deliberately, grossly (and probably criminally) negligent. They KNEW better, and they still violated every safety rule about firearms in film and firearms handling in general.
A sobering lesson for us all, especially those of us who use firearms.
Again, the PROVE procedure would have saved her life.