There aren't many things you can do in that situation. I think I would have stared the kid down. Just give the kid the meanest look I could muster, and just glare away. Let his imagination do the work for me. He'd either run off, or get in my face, then I'd just hold that same expression until he got bored and went away. Just to show that punk kid that not everyone backs down. If he doesn't learn that by the time he's a teen, he'll pick on someone with far worse intentions, and likely get shot/beaten/stabbed. You really do feel sorry for the misguided youth of America.