When I watched the video, it seemed the standing man backed away a step but just before the shot, he began to move forward again.
If the shooter had shot immediately after he pulled the gun, I think he would not have been charged as his attacker was standing right over him.
He who hesitates is lost.
Or, he(shooter) could mind his own business and not talk shit to strangers.
I watched the video a number of times in slow motion. The victim never advanced after the gun came out.
The shooter was being an absolute dick.