Alec Baldwin Mum on 'Rust' Involuntary Manslaughter Charge as He Returns Home

Alec Baldwin was in no mood to talk Friday as he arrived back at his NYC apartment building ... mum over the announcement he'll be prosecuted for involuntary manslaughter in connection with the fatal "Rust" shooting.

Baldwin shielded his face as he beat a hasty retreat inside. His lawyer has made it clear ... Baldwin will fight the charges, saying his client relied on professionals on the set and therefore the criminal charge is a gross miscarriage of justice.

Baldwin has some support from his fellow actors. Douglas Stewart, who shot a scene for "Rust," says in all of his experience in show business, actors have never been the ones to inspect the chamber of a gun. In fact, he says it's routinely prohibited ... and the actor's union has cosigned on that procedure.

Baldwin could face years in prison if convicted, but the D.A. hedged the other day when asked if prison time would be appropriate ... merely saying she wanted "accountability."

Baldwin is being charged both as an actor and an executive producer. But, Douglas Stewart told us Baldwin's E.P. title was really in name only, so he could get paid on the back end -- he did not have day-to-day responsibility over the set, which clearly had problems.

There's a lot of criticism over the charges, although Matthew Hutchins, the widower of cinematographer Halyna Hutchins who was fatally shot, is down with the prosecution.