If the same law applies to the cops as to the rest of us, then a passerby would have been justified in shooting all three cops to protect the woman - since the cops were in the process of committing a felony.
Each of those cops, including the chief, should not only lose their job but go to jail, and the chief should get the longest prison term of any of them.
What felony? Hitting a person who is actively resisting? "She looked 2 months pregnant? Uhhhh, do you have kids? 2 months pregnant, and "showing"?... In what world?
I suggest if that you see something like this and are carrying, that you probably should "stay your hand" unless you see an actual illegal act committed. From the video we see, there is hardly enough to know what went down.