There is a grand jury who disagrees with the version of events that you have imagined.
The grand jury is just as likely to be corrupt, and/or incompetent, and/or prejudiced, as the rest of the people involved with, and directed by, the systemically flawed justice system we have today. In addition, even assuming 100% competence on their part, the data that reached them can be (and often is) washed to provide a particular desired outcome.
The only takeaway I get from all this noise is that we'd be somewhat better off if police officers wore tamper-resistant AV recording gear when on duty (and in any jurisdiction that assigns them 24/7 authority, on duty or not, they should be wearing those cameras 24/7 as well. Personally, I think 24/7 authority is also a Very Bad Idea.)
There is no question that some individual police officers, and some groups of police, are corrupt. Given the seriousness of the authority and responsibility assigned to them, and their ability to ruin lives and families in a heartbeat, letting them run loose without any independent oversight seems like a very serious mistake to me, particularly now that monitoring their activities is well within the bounds of technical feasibility.
A bad cop is a horrible thing. It's also long past time for the blue wall of silence to creep its slimy ass into the black hole of history to join with some of humanity's other bottom-feeder behaviors.