I'm assuming he didn't know he was being filmed the whole time. I got confused as to how many people he was arresting, it seemed like anyone who turned up at the scene was targetted by him, including the guy with the hidden camera.

I'm thinking that behind it was a few seconds of the kid possibly winding the policeman up a bit, and he pushed it too far with the wrong policeman. I have been in similar situations myself, but thankfully receded at the appropriate time in all cases. It's no excuse at all though for they way the cop reacted though.

Even if they did set the incident up, or maybe set it up so as they could film themselves skateboarding past a cop and looking really decadent and it backfired, he still should be dealt with for this.