Watch The Last Word With Lawrence O’Donnell Highlights: May 26 | MSNBC

They fired the police so quickly because they were aware of the history such events like this have and they didn't want another  "National Day Of Outrage", centered around their city!  I also believe that they knew this is wrong and should be punished, but police powers being what they are,  there isn't the "official will" to move as "brutally" as the activity so richly requires, because of "technical command considerations".