I'd be curious as to what policy the cop violated.
IMO, getting out of the car with the gun already drawn could be seen as pretty questionable. You're not supposed to put yourself in front of a moving vehicle to eliminate your other options, thereby forcing you to shoot. If he's getting out without the gun, then it looks like he is expecting the driver to stop, even if he must then quickly draw, when he realizes the driver isn't stopping. He will have to articulate what he was thinking when this happened, because his perspective is what is going to determine if this is a legal shoot.
Edit to clarify: Because he did get out with the gun drawn, it looks like he purposefully put himself into a position where he had no choice to shoot, which would not be a legal shoot.
The chiefs analysis is wrong. He is armchair quarterbacking, when the courts (SCOTUS) has said that is not the right way to judge. The officer doesn't have to make a perfect decision, he has to make a reasonable decision. It doesn't have to be the same decision that another officer, or the chief would make, it has to be in the range of reasonableness.
Once again, regardless of the cops actions, we find ourselfve's here because the driver made a bad decision to drink and drive; Followed by another bad decision to run from the cops.