Police officers go through extensive psychological screening to be hired. They are well trained and there are laws in place to prevent injustice. I would surmise that the problem lies in what they have to face every day. If all the energy and focus could be spent positively on stopping crime and for communities to stop condoning violence and instead take a hard stance against criminals, I believe the situation would drastically improve. There are far more bad criminals than there are bad police officers. Yes, those officers who have crossed the line should be punished, but please focus where the real problem lies. ALL lives matter, so stop crime.
I think a hard look at statistics is in order. If police brutality is race specific, this is not really a police issue, but a national issue. Also, maybe more attention to the officers' mental health after years of dealing with the worst of humanity would be a good place to start instead of pointing fingers at those who risk their lives every day to keep the rest of us safe.
I think the root cause may be deeper. I am sure this is unpopular, but when you look at the statistics of whites and African Americans in prison it is much higher than other races. I suggest that this starts in the home with parents teaching their kids that criminal behavior is not tolerated. Maybe we should look at what Asian families are doing as the percentage of the prison population of Asian Americans is less than 2%. Maybe we should look at communities with no prejudice for ideas. If we are going to spend a lot of energy, let's really look at the statistics and focus our efforts where they are needed. If you consider there may be 8000 bad cops in the US (a very large number), that is 1% of the total officers. I think bang for the buck would be to stop crime before it starts. I recommend reading "Tipping Point." There is a very good section on crime in that book that digs at the root cause.
I guess you can look at the problem from the point of the police officers, but I think we would be better served looking at high crime and high prejudice communities too. It is a system. If you only try to fix one portion of a system, the other parts break. You need to look at the entire system when conducting root cause analysis. It appears to me that everyone is missing the forest because they are focused on one tree.