at what point did the guard tell the kid he was going to break his arm? to me that seems rather unprofessional. also the guard went after the cameradude, and I'm pretty sure he had no legal right to do so. The security guard's job is not to get in fight with kids, he's supposed to call the cops when shit like that happens. The guard knew he fucked up otherwise he would have called the cops. Instead he just stood there like a goof.
The security guard was obviously having a bad day.