OK, so you have proven that TM didn't have an obligation to retreat. Likewise, GZ fired in self defense *because* TM had no obligation to retreat and continued with the pummeling. But I should point out that not having an obligation is not the same as not being allowed to. Once TM had GZ down, he could have gotten up, given him one final swift kick and said, "stay down, you mother fucking cracker" and walked away. I have no obligation to stay at my desk at lunch, but that doesn't mean I have to go out. Likewise, I have no obligation to go out for lunch, but that doesn't mean I have to eat at my desk. It's a three state system. Obligated to stay and fight, obligated to leave once you have the upper hand, or free to choose your own path once you can.