Yes, the gunshots DID start before Brown ran away. They began before Wilson even exited the car. That's because Brown reached into the car and tried to take Wilson's gun. All facts that are confirmed by physical evidence (bullet hole in car, contact shot and powder residue on Brown's hand, and Brown's fingerprints/DNA on the gun).
But, by all means, DUmmy, continue to twist facts. It's kind of your (collective) thing.