I think we all know the answer to your question: He was in a motor vehecle with a loaded shotgun, with a chambered round, and it went bang. Safety or no safety, he should not have had a round in the chamber and he should not have had his finger anywhere near the trigger unless he intended to shoot something. Seems to me that the smartest thing this guy did was to stay away from firearms for many years.
When you deer hunt with dogs, the guns are loaded. Yes, you risk a hole in the floorboard, but as long as you keep the barrel down, there is no threat to life.
If your claim was correct, there would not be a single deer hunter in the south left.
Both the truck owner and my brother said the trigger was untouched. The only mechanical input was the gun being settled on a padded seat.
I have some experience with the same gun, and it does other weird stuff as well. I wouldn’t trust it for hunting or defense. Mossberg is a better gun pump gun.