I have always thought the cop probably did fear for his life, and that brown probably did attack him.
I've always thought the cop may have gotten heated after ass-whooping and chased it, pushed it, delivered headshot, and while it's very wrong, chalked that up to heat of moment after getting his face smashed.
This shady silence, changing little details, refusing to do an autopsy, taking 3 weeks and showing zero report... well, it's got me thinking there's another shoe to drop, another huge piece of info we haven't seen yet, but will. believe me, when the cops do things right 100%, oh, we ALL hear about it lol. They issue report fast and can't stop talking about how great a job they did.
Silence, that worries me... they are scrambling or playing politics, or both.