It was not involuntary manslaughter on Baldwin's part. It was literally set up as a shot to do exactly what happened. He was supposed to aim at the camera. He was given a prop which was declared to be a cold gun. From his point of view that means is it 100% safe.

The Assistant Director was a complete moron though. He never should have been putting a hand on a gun. That is only supposed to be done by the Prop Master or the Armorer. Period.