...Did they find the sandwich?
Shouldn't be that hard to find the truth here. Search the gun for fingerprints, see if you can tie it back to the victim apart from it being on the scene...try to find the bullets he allegedly shot...see if you can get a count of shots fired from witnesses and match it up with rounds missing from the cops gun...
At the same time, the local black community is not going to (nor should they) trust the local PD to provide an honest assessment of the evidence or the culpability of the officer. So, this is going to be one of those "relative" truths, no matter what. And that's a problem.