As someone that has been working around weapons for the better part of 20 years, I disagree with your statement of not being blamed.
It’s unfortunate yes, but whoever had that weapon in their hands and pulled the trigger should hold some blame.
If anyone ever hands you a weapon, movie set or not, it should be checked.
I do understand that it doesn’t quite work that way but that’s how it should be. Anyone handling a real weapon, especially during the course of ones job, should be required to go through training.