I do expect actors to be held to a minimal standard of competency when handling firearms on the set. That means they need to know what is going to happen when they pull the trigger, especially if they are pointing said firearm at someone else. Being an actor is no more shield from responsibility than being an absolute amateur handling a first-time gun purchase without any knowledge of basic firearm safety.
Obviously, this was an accident, I have no doubt, but there was a serious lapse in safety precautions, and ultimately the last line of defense preventing such accidents are the shooters themselves.