This guy probably doesn't train. Maybe he does... there's no evidence to suggest that he has experience. But he executes a text-book knee-on-chest out of sheer instinct, it seems. Oh, let's not just forget the one handed choke.
Either the assailant isn't working with much upstairs or he was intoxicated on something, likely both. It takes a special kind of stupid to try to punch someone with a helmet on. The rider did a great job of defending himself and his girlfriend.
According to the news story the assailant broke his ankle in the scuffle. He was not taken to jail and charges are pending review of the video evidence.