I submit to you that you do not know what happened. Don't feel bad- very few people outside of the 12 members of the Grand Jury have heard all of known facts of the case. I certainly don't know what happened.
But please keep this in mind. Things that you accept as fact are not really facts. Case in point: your assumption that Brown had surrendered. Some of the sworn testimony that was released tonight following the prosecutor's press conference indicates that Brown had not surrendered, and in fact was charging the police officer "like a football player" with his head down and fists clenched. And at the same time, as the prosecutor detailed in his press conference, much of the early eye witness accounts that indicated that Brown had surrendered did not hold up under further scrutiny.
As I said, I don't know what happened, but I think this is enough to move the narrative that Brown had surrendered out of the "fact" category.