If he sawed the barrel to less than 18" the guy had better have the punks parents return it to him disassembled - not real sure that would do it. I would suggest pitching the sawed off barrel into the nearest lake if it is under 18" then looking for a replacement barrel and stock. Look here
Beretta A301/302/303 Shotgun Barrels*|*e-GunParts.com .