I'm skeptical of both sides of this story. As usual, the truth probably lives somewhere in the middle, but we'll never know for sure what happened. Without Brown "going for the gun", the officer is going be some serious hot water, so we must be careful about accepting this as objective information. This doesn't make any sense unless the gun was already drawn by the officer. I just can't see a scenario where Brown goes for the holstered gun but fails, then officer draws the gun and shoots twice, hitting once in the arm.
More likely, imo: once the scuffle started, officer goes for his gun, Brown sees barrel of gun heading his direction and tries to stop it. Of course he should have just submitted to authority from the start, but he didn't and died because of it.
My take on the rest: Once Brown was shot the first time, he turned to flee but realized a moment later that would be a really bad move, turned around put hands in the air and started back towards the vehicle. Dumb move here, as he should have just stopped moving or laid down. Do not want to appear threatening at all in that situation. But....cop was still freaked out, adrenaline still pumping thru his veins, sees a really big black kid bearing down on him again and empties his clip.
For anyone who's ever been in a real physical confrontation before, rational thinking gets really dicey. Add a gun, and someone often ends up dead. Difficult to point the finger too hard at the officer, as he probably did feel like he was in danger (despite being the guy with the gun). Brown wasn't going to get his gun at the point the clip was emptied. Can't expect perfection from an officer in the heat of the moment, but a little more restraint would have gone a long way. Furgerson is a tinder box of racial tension (look at surrounding history of how PD was doing business leading up to this incident), and this obviously set it off.