A tragic story, and I doubt the father or the boyfriend will ever fully recover. But sadly, I think the boyfriend must have pulled the trigger. (a mechanical failure is incredibly rare) The big stand out for me was that he was showing off and fondling a LOADED gun which combined with the outcome means that he broke ALL 4 rules.per this article, it went off while he was putting it away
I chamber check a gun I simply move from one safe shelf to another... actually I chamber check any gun I pick up, even if I had just set it down a few seconds ago.
I couldn't imagine pulling out a gun to show someone without checking/clearing first.