I had a similar thing happen last week with a friend's son. The father and I were taking the son out to shoot, and he was shooting a .22 gallery gun. I was to his left, watching him. After he finished his string, he turned to ask me a question, and swept me with the gun.
Now this is also a kid whom I teach - he's my stage manager for school productions, but it didn't matter at that point. I immediately told him - a bit sharply - to keep the muzzle pointed downrange. He apologized, and I stepped over and was telling him to make sure the gun was open and empty before moving at all with it. I opened the action, and there was a .22 round sitting on the carrier. :nono:
Silly me, I thought I was making a theoretical point, and here the rifle was loaded - not just "every rifle is loaded."
I didn't ream him a new one, because he's a new shooter, but you can be sure I made VERY clear - gently - that he came one step from blowing my head off!
I don't think, however, that because he did it once he'll do it again. He's a bright kid, and I think that he was embarrassed enough to learn the lesson, and luckily (for me!) nobody got hurt.