If he was driving the BMW, the dumb ox needs to (1) spend the rest of his life in jail, and (2) forfeit everything he owns, or will ever own, to the families of these people. I drive that very stretch of highway every day - he needs to pay dearly for thinking his jollies are worth more than my life.
Again, this assumes he was driving - a fact we're not sure of at this point.
I think we can be pretty sure he was driving. He turned himself in, and if someone else was driving, he could have named him pretty quickly.
If someone else is driving my car and something like this happens with the police looking for me, it wouldn't take me long to start trying to clear my name by telling who really was involved. Unless I were actually the driver.