This paper(1) is by a Black economist at Harvard. On page 5, Blacks are 25% less likely to be shot, though they are more likely to experience non-lethal force. The paper concludes there are a minority of officers who discriminate.
I was quite surprised by that.
I also was curious about that because it didn't match my preconceived notions, so did a rough check of some of the crime stats myself(2). It seems about 25% of fatal shootings are of Blacks, which is about proportionately double the rate. But if you look at something like arrest rate for violent crime as a metric for encounters with police, they're a little bit over 25%, which would be consistent with the former paper's conclusion.
I have no doubt that in the past there was terrible discrimination, and that presently a minority of officers do it, which is still unacceptable. But whenever I see people talking about this topic presently, I never see facts or statistics brought into it and it comes off as hand-wavey virtue signalling.
1- http://www.nber.org/papers/w22399
2- https://ucr.fbi.gov/crime-in-the-u.s/2016/crime-in-the-u.s.-...