You have a few incidents, and many of these incidents were controversial (Meaning many on both sides), and officers getting off. SOME, and it is very few, should have faced time. But others the case was murky at best, and they didn't face time or lose their badge for good reason.
See, if the officers get off due to the Alton Sterling incident, many will complain they got a slap on the wrist. I don't see it that way, I saw two police officers doing everything they could to prevent it escalating to using lethal force. But I think there is SOME questionable things in the videos I watched, but a court is not going to convict them on those videos. You, and others, will consider them "getting away with murder" - I am waiting for more evidence on the other, I suspect the man had an itchy trigger finger. But I hold off my final judgement and wait for evidence, because it makes sense. Me making a conclusion due to select past actions is irrational and it does not help debate and it adds fuel to the fire within an already emotional nation.
And you're using a false equivalence here, everything coming out is that it was a peaceful protest. Shots were fired from a rooftop first, so they shot into a crowd of protesters and targeted innocent policemen/women. There is also evidence coming forward that a suspect admitted to this being a hate crime. But there is no evidence, as of now, that they were justified in the shooting (I can't see how there is anything that could come out saying they were)
This is very much the issue in these situations. I understand emotion, but it completely blocks rational discourse. This DOES NOT MEAN you don't try to minimize police brutality as much as possible, you still do. But there is a difference of keeping the problem in realistic terms and attempting to perceive it as an epidemic.