I honestly don't know what happened or if the shooting was justified. If I were on the jury I would look to the prosecutor and defense atty to make their case as to what happened. I would look to the Judge to instruct me as to the law. If the officer's actions fit the legal definition of justifiable self defense then I would not vote to convict. If it did not fit the definition and/or the officer was acting contrary to established protocols then I would vote to convict based on the law as delineated to me by the judge.
Absent being on a jury, I would form an opinion of justified self defense if the actions of the defendant would meet the reasonable person standard of a threat. You cannot shoot a person just because that person at one point resisted arrest or attacked the officer. In this case I'd need to see evidence that demonstrated to me that there was a preponderance of the evidence that Brown was charging the officer. That standard is insufficient for criminal conviction but sufficient for a reasonable citizen to form an opinion.
As it is (absent any other reasonable scenario) the evidence would need to show that Brown was charging the officer and at some point bent forward sufficiently for the officer's bullet to strike Brown in the head.
The notion that any perception on the part of the officer was sufficient to justify deadly force is not correct. It's far more complex than that.
WHAT’S REASONABLE?: SELF-DEFENSE AND MISTAKE IN CRIMINAL AND TORT LAW