I concur. It appears from the evidence that has been presented through the press, etc. that this guy is a loose cannon and totally lost it.
The defense is trying to present a case that shows he acted out of self defense and he felt so threatened by the other hunters, he had no choice to shoot them of "be killed" himself.
I can imagine that if I ever felt threatened, I would end up shooting my threatener in the back.
I would imagine due to the past history as you say of the Hmong groups and others not respecting landowners rights and the property of others, that the hunters had a few choice words for this guy when they found him in their tree stand.
Maybe, perhaps, they did fire a warning shot to scare him and maybe, just maybe he felt threatened enough to fire back but this relentless onslaught of murder transpired over several minutes of which time Vang had ample opportunity to get out of there. Afterall, he admits that he was on the ground and walking away when they supposedly shot at him.