Why was the gun being worked on without clearing it? Total malfeasance and deserves to be sued.
Do we know if it was a gun range employee working on the gun or maybe a customer fiddling around with their gun? That particular range also has a gunsmith in a smaller building next to the range house as well, but I wouldn’t think the gunsmith would make a mistake like that. I suppose its possible that a live round could be stuck in the chamber or the gun had a broken extractor. At this point we don’t know, but this is obviously why you always treat guns as loaded and always pointed in a safe direction.