I may be reading it wrong, but your first sentence doesn't make any sense. "All to blame" is the same thing as "completely his fault".
Dunn killed the guy. He didn't do it intentionally, but the fact remains that he was in control of the car making bad decisions. His friend should have been smart enough to know getting into a car with a drunk person is not a good idea, but I can only assume that he was drunk out of his mind as well and we all know alcohol does not improve your judgement. To me, saying that it was his friend's fault that he died is like saying it's a family of five's fault for getting hit and killed by a drunk driver just for driving on the same road as them.