That's really upsetting; I wish I hadn't watched that.
There was a case in my city a few years ago where police killed a 50-something man whose hands were cuffed behind his back. Supposedly he was grabbing for some officers' naughty bits. All the officers were completely cleared in the internal investigation.
In 2000, city legislators established a Citizen Review Board for these cases as a response to anger over several of these cases, as there was a very realistic fear of rioting. The FOP has tied it up in court ever since.