If he was shot 30 feet away from the police car then it's apparent that the 'attempt to take' - if there ever had been one - was long over and was unsuccessful. So the cop had his gun, Brown was unarmed and running away, and now we're back to why the need to shoot an unarmed, fleeing man?
an unarmed, fleeing criminal who just had a violent encounter with a cop
Was he shot 30 feet away or did he run and stagger 30 feet and fall?
Here's another scenario. The struggle could have moved from the car and continued over the ground with Brown still attempting to take the weapon away. None of us were there. We can only speculate as to what happened after that first shot was fired. I had to struggle to restrain convicts over my 25 year career in corrections. That struggle doesn't always stay in one place, and can end several feet away form the original site.