Repeatedly picking fights while armed like this guy reportedly did should be cause for the revocation of your carry permit. A carry permit is not a licence to go causing trouble. I don't think there is anything illegal about asking folks not to park in handicap parking, but if it escalates into an angry verbal argument that leads to someone getting violent he could be found at fault, IMO. All that husband did was push him away from his wife. Is that unreasonable?
Old man was perfectly within his rights to pull his weapons after the verbal argument was escalated to a possible assault by the husband, IMO, since the husband advance two steps towards him while he was down. But, when the husband saw the gun and RETREATED at least two steps back and half a step to the side I would argue that the threat was ended and shooting was no longer necessary.
At that point, IMO, shooting the retreating threat became illegal. I don't know where some of you got the BS idea that pulling a gun and then not shooting is a crime (brandishing.) If pulling your gun is enough to end the threat then you can't legally shoot. The Stand Your Ground law says you don't have no duty to retreat before using deadly force, and that you can use deadly force to protect property. It doesn't give you the right to shoot someone retreating even if they did push you to the ground, especially when you are in a public parking lot picking fights.
For this to be a legal shooting we would have to believe the old man REASONABLY believed his life was in danger at the moment he shot. I do not.