Check out this video from CBS2Chicago. It was interesting and since I've been out of public school I get the feeling that some public school administrators, even in some of the more affluent suburbs can be prone to over-reaction. But I'll let those who see this video decide that.
Still why expel a young man who ultimately did the right thing and the gun wasn't even his. Though he also could have just left the gun there and told security. I won't second guess him though.