I don't think we see enough of the event to use the video as the basis for any conclusions about good/bad shoot. I AM surprised, however, that the Atlanta PD acted so quickly to make their call one way or the other. Though they claim the shooter is not a police officer, it may well be he was an undercover officer or a store security agent.
I am not surprised at all. Look at all of the victims who were witnesses who have the armed guys to thank for saving them. They probably all told a very similar and very convincing and likely very truthful story.
Besides, the cops can make the call very quickly. We see it often. Doesn't mean the DA will agree, but for the time being, probably nothing conflicted with the notion of it being a bad shoot.