The general rule of thumb used to be that a person walking away (or running, as from police) is no longer an attacking threat to anyone. Particularly if unarmed.
That was surely not a shot fired in self defense. It was payback for pushing him down. An escalation no doubt, and unnecessary. The stand your ground law surely wasn't intended to sanction unnecessary killing.
that's how I look at it. this was not self defense or fear for one's life. This looked strictly like a guy looking for trouble, finding it and taking out his issues about handicapped parking on someone.
If the guy who pushed was going at the guy on the ground, yeah, I could see fear for his safety. that wasn't the case.
Also, what makes me see this as non-self defense is that there was no time between pulling out the gun and the shot. There seems to be no window of opportunity for the shover to get in his car with his family and leave or anything to warn the guy to go away or else he'll shoot. it's not like the shover had a gun or another weapon that he'd use. The shooter seems hellbent on shooting the guy that shoved him.
I hope he's prosecuted for murder. Killing someone over a parking space is just inexcusable. shove or no shove. I would not be surprised that if nothing legally is done to the shooter that an acquaintance of the victim parks in a handicap spot to bait this killer into a confrontation and shoots him claiming the same protection under Stand Your Ground.