I haven't seen or read anything about this other than what is posted here but IMO, if the shooter had been drinking, he's in a bad way legally. Additionally, if the argument had been carried on for awhile, I think the shooter, as a legal carry, had the responsibility to defuse the situation, perhaps by leaving before things got to the point they did (at least that's what I would have done). This looks like: DRINKING + ESCALATION = NO GOOD OUTCOME.
Again, there is probably more here than meets my eye, but that's my initial reaction.
Prov. 27:3 - "Stone is heavy and sand a burden, but provocation by a fool is heavier than both"