Brown robbed the place and the cop heard his description soon after. That's what the cop's proxy is saying. So both the cop and Brown knew what was up when they locked eyes. The cop's saying Brown charged him and tussled for his gun with him. Brown gets up and runs away. Protocol says the cop needs to stop Brown, so he shouts 'Freeze'. Brown turns and charges him again and the cop opens fire. The cop's proxy said he thought Brown must have been high on something, 'cus he just kept coming.
This narrative is supported by the first autopsy and the requested second autopsy. They both found that Brown was facing the cop when he was shot (so he wasn't running away, like some claimed). Now though, Brown's family is calling for a THIRD autopsy - which is unprecedented.
What you've got here is a group of people who decided from the get-go that they knew what the correct and real storyline was. Now, that they're starting to be disproven, they're at a point where they need to either accept what the real facts of the case are OR just continue to use it as an excuse for looting.