I don't believe it. Of course there are many types and systems of guns, but most pistols take a grown-up man to comfortably ready it for the shot. You may say "Ha, the guy just cocked the trigger and left it this way", but it sounds even more unbelievable. Because why would you cock the trigger of a loaded gun? While cleaning, you might do that to CHECK IF THE GUN IS LOADED. And while you do that, the only cartridge left would be ejected. Unless that is a revolver or a musket, or blaster-shmaster or something else very strange.

Strange story. I smell a lie.