Simply put, this is the result of the ages old American policy of segregation, lack of social investment (while they invest trillions in Iraq and Afghanistan), racist housing and loan policies, severe lack of education and school funding, unemployment, aggressive racism (seems like a there´s a region and mindset in the USA that has never forgiven blacks for getting their freedom) . . . and of course with these conditions, these areas are vulnerable to crime and violence and drugs. And it´s all left to a questionable police force that often must act as a occupying force.
And when the shit hits the fans, you´ll get the old refrain of, "you see, these people are animals." As if it were a self fulfilling prophesy.