I wonder if the logic of carrying the BB gun is for intimidation. If he gets in a jam, he pulls the gun, gets the home owner to back off giving him (the kid) room to retreat and get away. And, if he gets caught, well it's only a BB gun and he didn't intend on hurting anyone. Yeah, right.
I think the kid should learn there are consequences to everything you do, included getting killed for B&E. Run him through the court system and let him know that's another consequence of poor decisions. Congratulations junior, you now have a criminal record.