Well, there is the whole idea of disproportionate force...
From the shooters perspective, what kind of dipship sociopath is willing to live with taking a person's life, a person with kids, cause he was following him around and invading his space? Personally, I am not willing to live with that.
Just kinda gotta point something out here.
If some drunk assbag is getting all up in my grill, I'm not going to ask them whether or not they have a wife and kids so I can decide an appropriate level of force. I don't think anyone will.
I don't think the shooters actions were justified at all, but let's be real here--maybe, just maybe the drunkard should have thought about the fact that he's a father and not acted like a complete dickweed that at best, gets him sent away from his kids in the drunk tank and at worst (like what happened) got his ass killed.
It's 2016 FFS. The world has plenty of dipshit sociopaths out there on hair triggers waiting for justification. You go around beating your chest, drunk or not, and you risk setting them off--and whether or not they're charged with manslaughter or justifiable homicide makes little difference to the kids who are without a father because their father decided to get drunk and act like a schoolyard bully.