If I read this correctly and watching the video - the shooter went on another's man property. Then he displayed or made known he had a gun. He refused requests to leave another man's property.
There was a police car already there. He didn't go over to it.
He announced SYG as it is a magic excuse. He announces that he is in fear of his life as a magic excuse he got from some gun source - when he could leave. The victims clearly respond to a threat from his gun by saying they will get their own. Stupid drunk behavior - they should have simply told the law there is a madman threatening them with a gun.
He feels he can reason with the alcohol fogged reasoning of several people. Or was he posturing for some bizarre reason.
This is exactly the problem with the misinterpretation of SYG that we are seeing from some. It is also an indication of a lack of understanding the use of the firearm which is not to SYG but to protect you. Leaving is a better option. Not staying there and instead showing off the gun as it will deter the irrational (sound familar from another thread).
For what it is worth - it seems the shooter wanted the confrontation and was driven by some stupid dominance factor to stay there. Or he was thinking he had an excuse to shoot? And wanted to on some level?
Did he think he was justified? Even if a group charged him - recall (if I read it correctly) he was on another man's land acting threatenly with a firearm. Did they not have the right to SYG which trumps his non-existant SYG claim?
So my quick take (and facts can prove me wrong) that he is to blame.
Here's a good take from Mas Ayoob