And what might have happened when he realized the reason he couldn't pull the slide back was because the safety was on, took off the safety and went to pull the slide back?
Couldn't the same AD have happened?
If he took it off safety, and pulled the trigger, Boom!
Might have been a clue that the gun was cocked and locked because he couldn't pull the slide back.
I don't think that's how it went down. He just thought it was empty, and pulled the trigger.
But again, if the safety was on, the trigger would not have fired the gun.