Looking at the traffic stop rates in Ferguson by race and the data regarding the higher rate cops kill blacks during arrests and the fact that the cop was a human, one can assume with reasonable probability that race was a factor in the interaction between Brown and the cop.
Not sure if your claims are correct that Ferguson police subject blacks to a disproportionate number of traffic stops, or that police kill a disproportionate number of blacks during arrest, but I don't think either of those things proves overt or inherent racism.
Perhaps not at the precise moment he pulled the trigger, but in the way the two initiated contact and subsequently escalated.
The way Brown and Wilson "initiated contact" seems pretty well uncontroverted. Brown had just finished robbing a store, was walking down the middle of the street, and the officer told him to get on the sidewalk. That doesn't sound very racist.
As for how the conflict "subsequently escalated," it seems most likely that Brown assaulted Wilson, given Wilson's seated position in the vehicle and Brown's assault of the shopkeeper just 10 minutes prior and otherwise deranged behavior (rob a store, assualt the shopkeeper, then stroll down the street and refuse to obey an officer). Again, not seeing racism here on the part of Wilson.