Some news stories about it:
http://www.latimes.com/local/lanow/l...622-story.html
I saw a thread on reddit earlier. Evidently they started recording because the motorcyclist was first on the other side of the car, they were kicking and screaming at eachother. Then the motorcyclist went to the other side of the car, and the video shows what happened next. I think @
MrAtom has it about right.