Because black on black crime is the direct root of the police contacts and injuries.  Black shootings by the police are a symptom of black on black crime.  Gangs kill each other and sell drugs and other crimes, the police respond to those crimes as demanded by the community.  The police get no cooperation from the community and have to contact yet even more people to identify who is involved.  That contact infuriates those people and you get confrontation which leads to more injuries.  Is it not that straight forward, nah it has to be a bunch of cops who are racist.