Reading the online news article, and taking the comment by a woman claiming to be a friend of one of the involved females into consideration, it seems as though the attacker had already brandished a knife, and had laid hands on the shooter's friend(s).
a reasonable person in the same or similar situation would believe that (a) the person killed intended to commit a forcible and life threatening crime; (b) there was imminent danger of such crime being accomplished; and (c) the person acted under the belief that such force was necessary to save himself or herself or another from death or a forcible and life-threatening crime. Murder, mayhem, rape, and robbery are examples of forcible and life-threatening crimes.
I'm not sure how VA defines mayhem, but there was supposedly choking involved, so murder was a possibility, and supposedly keys/cars were stolen or attempted to be stolen, so there was robbery involved. The only remaining requirement for justifiable killing is that the shooter acted under the belief that such force was necessary to save himself/his friend from the above. If their independent accounts given to police, and possible testimony in court, corroborate that he did act under that belief, then I would imagine he (the shooter) would not be charged, or be acquitted. It certainly appears (given the available information) that it was a justified action, assuming our understanding of VA law is correct.
The shooter's decision to leave the gun in the car when he's at the bar might go a long way to show responsibility, whether he was drinking or not. Or it might not even come up.
However, that's a legal discussion, and this is the Tactics & Training forum.
Regarding Tactics, when they saw that this guy was outside in the parking lot, after having an incident already occur, I believe they should have gone back into the bar and called police, wait for police to arrive, and then driven away with no altercation. File a civil restraining order against the attacker the next morning to document the aggression. Everyone goes home in one piece. While some might ride the "one less idiot on the streets" bus, I don't personally know of any one human who has been appointed judge and exocutioner of the free world.