“I’m sorry, but I don’t understand this. Can somebody explain how this happens?”
Recoil twists the gun upward so that it is pointing back at you at the same time you tighten your grip on the gun (and trigger) while trying to get control. Hard to believe that it can happen with a double action revolver but apparently it can.
Having owned and fired three barrel lengths of this gun I have ample doubt this could happen especially to a Command Sgt Major. Even a desk warrior has had considerable shooting experience - especially a 23 year vet.