What really happened could be these 4 versions:
1. Z followed T, T got angry then attacked Z, Z killed T out of fear for his life. This was the version the jurors went by then made the not-guilty verdict.
2. Just like version 1, but Z knew his life was not in danger, he still chose to shoot T to death.
How do you prove Z was or was not in fear of his life before pulling the trigger? So in this case, Z the defendant received the benefit of doubt.
3. Z provoked T verbally so T attacked him, then Z killed T.
It is not impossible. I think it is very possible.
4. Z doesn't like black people, when he saw T in the neighborhood, he followed him, killed him with a gun, then hurt himself by punching self in the nose, pounding his own head against the pavement -- note that police arrived at the scene shortly after the gun went off. Z had to do all these in such a short time, not to mention he called police before the alternation and passed lie detector.
Version 4 is still possible but not probable.
What does your common sense tell you?