All 10 cities that saw sudden increases in homicide had large African American populations, he said. While it’s not clear what drove the increasesLet's see... I'm a white cop patrolling a black violence prone neighborhood. Do I risk my life stopping black-on-black crime, or just let it go, especially knowing I'll get no support from the media and Feds, White House on down? Seems pretty clear to me.
Also worth noting is blacks commit violent crime at a much higher rate than whites. The stat is hard to find and I once calculated it myself. IIRC it's about 30x the white rate.
This fact-based article says "A black male is 40 times as likely to assault a white person as the reverse."