I don't know the answers to the following questions. I am not versed in local civics and policy where I live, and should be. The questions would be relevant to any city with a police force.
Who do the police answer to? To the mayor or city council? Are there state statutes that regulate how police departments are run?
Your and my elected officials allow this.
A legal team and public pressure where the public dictates the rules and procedures to a PD is one of few ways to effect change, adding on to blues' suggestion of highest prosecution. Qualified immunity goes away and the police department becomes a transparent and trusted element of daily life.
I won't say "We need to change......, or What we need to do is......." I want to lead the change.