This is 100% on Baldwin.
He aimed a firearm at people and pulled the trigger.
It’s irrelevant what he may have thought. This is a negligent discharge at the least and therefore negligent homicide.
No it’s not.
He was handed a weapon that was supposed to have been checked
out by a prop person.
They hire a person to take care of this. The staff accepts
that they are the set expert on such matters. It is accepted
that the gun has been rendered harmless when the actor takes
possession to film the scene.
It isn’t Balwin’s job or responsibility to recheck it.