A claim by his lawyer that he didn't know is heresay. It is unbelievably easy  to say "I didn't know" with no ability to refute because it is is someone's mind. The question is why buy a gun " for protection" if it wasn't loaded? Why buy the gun and not ask if bullets are included knowing the kid could not get them legally? Did the kid ask how the gun operated as would be reasonably be expected of a 13 year old without " gun experience". Any reasonable person would ask these questions.  Until someone can answer these questions credibly, I believe he is lying to mitigate his own culpability.