You can start by identifying every cop who has been involved in violence and brutality, and firing and replacing them. Or don't even replace them. Hire professionals of other types, like social workers, to be the point of contact in many cases.

But I think, more important, would be to partially disarm PDs. Pretty much all SWAT teams need to be disbanded (along with Federal SWAT teams that are part of almost every federal agency - the department of education has a SWAT team). And reduce the arms carried by cops. Most should be disarmed, with the ability to arm in a crisis. In some countries, like Iceland, police carry their guns in a locker in their vehicles, and they call in to headquarters to get a code to unlock them. That way they can get them in a violent situation, but there will be a record of the use, and it provides a disincentive for careless use.

Of course, part of the reason cops are so heavily armed is because the population is armed. If you live in a gun culture, you should expect to have gun deaths.