If the cop reaches the point where he legally decides to fire one round, he is legally able to fire 100 rounds - whatever it takes until the person is no longer a threat.   Cops get hated on for overkill, but if the person is still standing, still a threat, still swinging, yeah, empty that gun.  Wouldn't surprise me if the cop put 5 bullets into his own dashboard and 6 into the victim.
I haven't heard full story yet - was Brown inside or outside the car?  
I haven't heard any inconsistencies in the shoot itself.  It's just the changing of why he approached him - that bothers me.  The minute we say "I don't care why police stopped a person" then we give them permission to STOP US for no reason... then just make up a reason, change it when that one falls thru, etc.  Then cops start making up reasons for tickets, planting weed on people, etc etc. 
Locally, we had a cop threatening people with "Do I smell weed on you?" to anyone videotaping an arrest/beating they were delivering.  It was a fake threat to scare them off and violate their rights.  Same way a cop told me when I was 18, "any more lip out of you and I'll write you a seat belt ticket" when I was 100% buckled in.  That'll come around one day.