"...the gun fell and went off". I started to make fun of him for carrying an antique but did a web search and found this article by Massad Ayoob:
Tactical Life Dropped Gun Inertia Discharge
If he had one of the guns that can discharge if dropped then he should not have had a round chambered or should have engaged the manual safety if not a revolver. Regardless it should have been in a holster more likely to keep it from getting dropped. I realize this is easy for us to say and as the cliche goes hindsight is 20/20 but any event like this adds fodder to the anti-gun side.