It seems that no charges will be filed in the matter of a shooting death at Colorado's Rampart Range.
So, the gun suffered a mechanical failure which caused it to go off. Okay, I buy that. Happens sometimes, due to failures in maintenance, design, or some other failure. But that does not excuse the shooter from fault. Whether or not he pulled the trigger, he pointed a gun at another person, and that gun went off, striking and killing his friend.
The Four Rules are sacred and inviolate for a reason. This shooting involved at least a violation of Rule 2, and also, I would say, Rule 1.
The Rules save lives. Follow them and live.