That's tragic but why was he cleaning a loaded gun to begin with?
One of my old firearms safety instructors almost died from a simple, stupid mistake. He ejected the round from the chamber, then removed the magazine, completely forgetting that he'd chambered a new round. He then proceeded to clean the weapon and ended up putting a bullet through his own abdomen. Fortunately, he was able to receive prompt medical attention and survived.
All guns are loaded all the time.