Lucky cop.
We had a case like that in Pittsburgh several years ago in which the cop was dragged for far more than a few blocks. It was only after he shot the driver and the passenger (while being dragged) that he was able to stop the car--ended up very badly injured but lived. The next day, you saw the perps' mothers on TV crying that he shouldn't have killed "their babies."
Sounds like attempted murder of a police officer to me.
Book him, Dano!