If you survive violence at the hands of law enforcement and are not convicted of a crime, or if you don't and your family wants to hold law enforcement accountable, then the first option is to ask the local public prosecutor to pursue criminal charges against your attackers.
Depending on where you live could be a challenge, given the amount of institutional racial bias in the justice system, and how closely prosecutors tend to work with police departments. After all, if prosecutors were going after police brutality cases aggressively, there likely wouldn't be as much of a problem as there is.
If that's fruitless, you would need to seek the help of a civil rights attorney to push your case in the the legal system and/or the media. This is where a lot of higher profile cases like this end up - and often only because they were recorded on video.