The general public doesn't understand how a movie set works, especially when firearms are being used. The armorer and his/her team are completely in control of all weapons. An actor should never check a gun, chamber a round, etc., UNLESS it's called for in the script. If an actor mishandles a firearm in any way, the Director or armorer can call cut and the armorer would then collect the firearm, recheck it, and then hand it back so the scene can be filmed again.
The really big question, in this case, is how did a live round get not only on the set, but in the gun? That's a HUGE no no. Hollywood movies feature firearms all the time, and there's a reason why accidents are so very rare.
Baldwin may be held responsible for squeezing the trigger, especially if the scene didn't call for him to do so. Another big worry he has is his role as Executive Producer. He had skin (money) in this movie. If he cut any corners, and it can be proven, he'll be in real trouble.
My understanding is that they weren’t even shooting a scene, just a discussion of how the scene should play out (don’t really know, I wasn’t there).
I read that Baldwin was a little irritated with the time everything was taking and being the smartass that he is, pulled the gun out of the holster, aimed at the director and shot her.
Guess we won’t know until all the Hollyweird Weirdos have had their chance to LIE to the prosecutor.
But if it did happen as I read, that would make it NEGLIGENT HOMICIDE wich carries a greater penalty under law.