If Baldwin is prosecuted criminally for this it'll be because of his role as Producer. Lots of people don't want to hear this, but normal gun safety in the real world is different than on a movie set. Movies hire professionals, usually two or three per film, to assure that things like this don't happen. The actor's job is to act, not check weapons. If an actor begins fiddling with a firearm the Director would most likely yell cut, and then have the armorer re-check the firearm. Baldwin, however, was a Producer on this project and there are rumors of people leaving because of unsafe conditions. If that's true, Baldwin could very well be charged criminally. Expect A LOT of finger pointing as the heat get turned up.
I would agree, the fact he pulled the trigger will not bring any serious criminal charges.... only way he’s going to face murder/manslaughter charges because he pulled the trigger would be if he knew that the gun was indeed loaded and capable of killing.. which no one, not even the most ardent Baldwin haters are suggesting.
However, if it is found that the entire production had a culture of lack safety that contributed to the death, and that Baldwin, as producer, was actively involved in those decisions.... then he could face some criminal charges.
But the fact he pulled the trigger himself, nothing in the direct chain of events that lead to the death were because he personally did something wrong as an actor.
Saying he is guilty of murder/manslaughter because he pulled the trigger, would be like saying the following...
You took your car to have its brakes fixed, the mechanic told you he fixed them, you drive off and later try to stop but your breaks do not stop you because the mechanic failed to fix the brakes properly.. you end up running a redlight hitting another car and killing someone.
Are you guilty of manslaughter/murder? No, your mechanic is.
Those arguing that Baldwin should be charged with murder/manslaughter because he pulled the trigger, is the same as arguing you committed murder/manslaughter because you drove your care without personally verifying your mechanic did what they said they did.