I found a news article that attempted to relate what happened in this incident. It was 3 white guys. HOward, the deceased person, was arguing with the father and son (Millers) over a box mattress found in an alley near their house. HOward wanted it in the dumpster the father and son did not.
Howard threatened the Millers with a baseball bat. The millers shot him 3 times.
Those seem to be the facts.
It sounds like the State of Texas is taking the position that the MIllers should have fought a very large man with a baseball bat in his hand and not shot him.
What a foolish thing to argue about. So sad.