The gun was likely never dropped. The "I dropped it and it went off" is a bull story told to cover up grossly negligent behavior. The kind of behavior you typically go to jail for.

Most of the time, the "dropped gun that went off" only goes off when someone tries to catch it or pick it back up.

Hence why your friendly neighborhood RSOs typically insist on picking guns up themselves, rather than letting the shooter that dropped it do so.