As to "able bodied people" parking in handicapped spots, honestly, you cant tell by looking, i know 2 people, one you might notice something wrong, and one you might not, both would get out of the car walking with no assistance, and appearing to walk fairly normally. My wife is one of them, she has brain damage, actually missing part of it, that pretty well qualifies her to be labeled handicapped, she has unending vertigo, almost no use of her left hand, limited control of the left arm, but you would see a woman in her mid 30's who looked fit, getting out of a car and walking, with just a minor shake to her gate. Her father has had several heart attacks and has heart disease, for all the world he looks like just a elderly man, but, his condition limits how far he can walk without resting. I'll totally admit, i used to see people just get out of a car from a handicapped spot and go walking off as a normal person, and was like anyone else, wondering why that totally normal person was parking there, then i learned, sometimes what you see, isn't what it is. Even a young person could have hidden issues that warrant that spot. Not all handicaps that would get you the permit, are outwardly visible.
Now all that said, looking at the video, the shooter was arguing with someone, and another person comes out of nowhere and shoves them hard enough to send them rolling, with no apparent warning. 20 years ago, i doubt i would have thought much of it, and would have thought a fight was about to get up, i might take my licks in this fight, but it wont go to life threatening, its just possibly going to hurt, these days however, more often then not (mainly cause just a fight isn't reported in the news) you hear about something like this going to the person who committed the assault continuing the beating till the other person was dead. So it is believable that getting shoved out of the blue that hard puts one in fear for their life.
Cant say without being in that situation what i would have done, cause we do not see a lot of what was going on, the woman claims the shooter threatened her prior to this, so a history might exist, might be she made that up. no way to know for sure.