Nah, when a citizen gets murdered, there's supposed to be a trial.
Okay. You're alleging racist treatments of minorities based on prosecutors failing to indict cops who kill black people.
There's supposed to get a trial when a prosecutor thinks that he can convict the guy of some crime. "Police officer shoots random innocent in what appears to be a tragic accident possibly involving negligence" is apparently not one of those cases, for some reason or another -- probably the cozy relationship between prosecutors and the police, which is dubious enough.
But I want to contend that it's not really racist: they really wouldn't hold a trial in a similar case if the guy shot was white, and if you keep playing at it for racial reasons you will fail to effect meaningful policy changes that will address the issue, which would be more unfortunate for minorities than it would for me or most Slashdot readers (because we're demographically less likely to come into contact with law enforcement, in part because we're fancy computer programmer types who make a lot of money and can afford to live in neighborhoods which aren't riddled with crime).