Didn't have sound on the video, my guess is that the kids were acting unsocially in public and were bad mouthing the police officer, my guess is that he did his job which was to protect the public place from damage and prevent trouble and intimidation for ordinary pedestrians. Instead of moving away from the scene other skateboarders just gathered up around the police officer, he was out numbered and probably felt intimidated, he did his duty in restraining the youths, if they cooperated with him he would not have to use physical action against them. Edit: And also it's disgraceful how they put up the officers personal details on their website, I bet some of the youths will cause trouble to him just for doing his job.