OK, I think the Millers are going to jail. Not for shooting the dead guy. But for putting the gun to the head of others at the party. That is against the law. And you can do time for that.
It seems the Millers have a few issues. First they were in their neighbors yard. Its ok to warn someone that they have lethal force. And to make sure they keep a distance. But that does not give you the right to threaten. And to put someone’s life in danger. Or even to come into someone’s yard.
But if the story is accurate. A bigger man who is angry and wields a baseball bat, is a threat. And you can blow him away if he approaches after a warning.
Agreed about the guy in the orange shirt, but if you continue firing when the man is down you mean to kill him and are no longer protecting yourself. I count the four shots two of which are from the 12ga. the guy was surely down and no threat when the four shot was fired and most likely down after the first two shotgun blast.