We are handicapped by information provided by both sides of the issue as well as how the information is structured for our consumption. But these seem to be the salient points:
Mr Scott is a convicted Felon. Mr Scott is on medication for a TBI
Mr Scott at some point returns and re-enters his car
Mr Scott re-emerges from his car, his car his right pants leg is hung up on an ankle holster that appears empty
Mr Scott does not have his hands in the air
Mr Scott appears to have something in his right hand
Mr Scott's wife "Don't you do it Keith" which obviously the officers are hearing
Mr Scott's family are given access to police video a day prior to public release
After the video is released publicly the family and their attorney state "...they do not know enough now to form an opinion on whether the officer ...should be charged"
The simplest answer is he had his ankle weapon in his hand and his wife knew what he intended. IMO, righteous shooting.

Black Victim/Black Officer.....Immaterial.