Joking aside,this pic is disturbing. Why would you keep something like this around?
From what I understand, the shotgun was "cruiser ready", which was a mistake to begin with, and was supposed to be bagged. The young man saw that the mag tube was full and decided to unload the gun. Him not being totally proficient with firearms, he tried to unload the gun by cycling the action a bunch of times. Evidently his finger was on the trigger and the ND happened.