I feel in my gut, not know, that it likely played out like this..
Officer grabbed Mike's arm from inside his cruiser. Mike punched Darren in a successful attempt to get free. Mike then walked away, Darren gets out of the cruiser, seeing red from having his authority disrespected by a fist, draws and fires in anger.
What if Michael's fingerprints are on the cops gun?
Lets see where we are at when the cop is seeing red...
Suspect has committed Felony strongarm robbery
Suspect has resisted arrest
Suspect has committed Felony assault on a police officer
There are others such as blocking traffic, etc..
The only question is whether Michael Brown charged the cop at the end of his life. I think Michael Brown woke up pissed off at the world. He went into a 7-11 and saw something he wanted and took it. When someone tried to stop him he intimidated and pushed them.
When the next person challenged Michael Brown he attacked that person who happened to be a cop. He slammed the door on the cop, he then slammed it again and punched the cop and tried to take his gun. During the struggle the gun went off and it just got real.
Him and his buddy run a short distance but they got a cop pointing a gun at them. Maybe a shot went off, maybe not, I dont know. Whichever happens they stop. Michael Brown is just pissed off at the world and this cop is in the way of him getting what he wants and he doesnt think the cop has the balls or the right to shoot him so he is going to take him down and then go home and smoke his blunts.