The available evidence as of now most certainly refutes what you are saying. It will be more certain when the coroner releases its report showing the single fatal hole in the front of Mr. Brown's carcass, fired at very close range, while Mr. Brown was atop the officer, pushing the officer backward into the police car pounding on the left side of the officers head, while trying to get the officer's handgun.
That is a very substantial case for the use of deadly force in self defense. The disparity in size justifies the use of deadly force in self defense. Mr. Brown (at any size) as the aggressor justifies the use of deadly force in self defense. Mr. Brown as the aggressor, with an accomplice close by, justifies the use of deadly force in self defense.
Even if Mr. Brown had ceased his aggravated assault and was trying to flee with one hole in the front of his carcass, the use of deadly force was justified (from any direction) to stop this thug who had already proven himself to be a threat to the public safety.
For one thing, if the shot to the front, the first shot, was fatal, I could understand this killing. That’s not the case.
I just disagree with you that there was any further danger to the cop. The evidence isn’t pointing that way. I know you want to believe that, but there isn’t.