In retrospect, my guess is the officer wishes he had, too. Brown was walking away, according to the source. The officer drew his gun and ordered him to freeze. He'll live with the consequences the rest of his life.
King, you may be right, the officer may think that. The problem is that in a society governed by rules and with men and women charged with enforcing those rules, it was his job to do something about the person who had just assaulted him (if that was the case).
Police officers are not in the business of letting criminals walk away. We ask them, in fact, to ensure that does not happen, by whatever lawful means they deem necessary at the time.
