When a gun is discharged by mistake, I have a hard time believing the "cleaning" excuse. If someone is knowledgeable enough to clean a gun, wouldn't they also have the knowledge to unload it? Maybe, maybe not.
Anyway, here's my addition...
In my hometown, back when I was a kid, there was a cop who fired his service revolver through the walls of his house and into his neighbor's house. This happened late at night. When his fellow officers responded to the 'shots fired' 911 call, he explained that he was cleaning this revolver and didn't know it was loaded.
My dad told me that the cop was probably quick-drawing in the mirror after having had a few beers that night, and inadvertently blew a hole in his house.