So blacks kill each other a lot. Not sure what you mean when you say they're responsible 88% of the time. Criminal arrests doesn't show comparative criminality - it could be a sign of systemic racial bias. And did you look at comparative conviction and sentencing rates based on race?? 

Fewer than one in three black people killed by police in 2016 were suspected of a violent crime or armed. And one study said “when factoring in threat level, black Americans who are fatally shot by police are, in fact, less likely to be posing an imminent lethal threat to the officers at the moment they are killed than white Americans fatally shot by police.”