Here's another thing folks are conveniently skipping over... one of the following has to be true:
A) He fled because he was also drunk (which is most likely scenario).
-or-
B) He was sober and willingly and knowingly raced this girl that was well over double the legal limit to drive (so no way he didn't know she was drunk), all at very high rates of speed through traffic and residential neighborhoods. And then fled the scene, sober, while his friends were dying.
It still wouldn't be acceptable, but this is way worse than if they were just out on some flat, long, straight, deserted country backroad having a drag race.