This fellow is named Joseph Smith, his father is the Deputy Director of the Public Security Bureau, John Smith. Relying on his father's power, this guy is usually very outspoken. Although he has not committed any serious evils, he has bullied many, and whenever trouble arises, the local police stations and branches all give face to his father and do not deal with him harshly.
Moreover, Joseph Smith's mother is an extremely protective woman. Whenever there's a problem, she will side with her son, which makes him even more fearless and reckless in his actions.
Today, he hit a taxi driver, which for him, was a trivial matter that he did not take to heart at all. Coming to the police station was just to show respect to the Director and for those around, to prevent triggering public opinion, since the internet is quite powerful nowadays.