Not sure what model the revolver is but my Vaquero has a safety that would stop that from happening. If that guy was a single action and he pulled the hammer back and dropped it, it might fire.....maybe?
Pretty sure I read that for the shot he was in a seated position in a church pew, and had to cross draw the revolver from his left side using his right hand, sweeping towards the camera and cocking the trigger at the same time. So he would end up pointing into the lens with a cocked gun. He says he fumbled the cocking motion and released at then end of the sweep before it had latched...
Apologies that I can't remember where I read this sequence of events, but it does seem to explain most of what happened - except for the loaded firearm part of course
I have absolutely no idea/opinion on whether the above is true or even possible, just leaving it here for the guys who do know about this stuff to comment on please
Baldwin says he won't do another movie unless he's allowed to assassinate the cinematographer and incapacitate the director.
