You did the right thing, except I would have taken the dogs out of his reach and told him to back off. Some kids, especially boys (sorry) can be cruel and unthinking enough to pull a prank that can hurt an animal because they think it will be funny. They don't think before they act. You're lucky your folks came when they did if you were ready to deck the brat. I wish I was young enough to get away with something like that myself sometimes.