[Thor]

The only way I can see making it discharge accidently, assuming all the parts were not worn in the sear/firing pin engagement area, is to take off the sideplate. That covers the section of the sear bar that can be pushed inwards to make it fire. I he had anything else in his pocket at the time and the safety was off, I could see how something might push against the trigger and cause it to make the gun fire while in his pocket. Or maybe he was used to handling a loaded 45 that has a grip safety that the Luger probably didnt have.