There will be no change without re-structuring the police unions. It's the unions that protect them and their jobs when they do stupid shit like this... this went beyond the point of where a union could protect this cop, but many incidents similar or worse have happened and the union is there with good lawyers to protect them. Police are a brotherhood, similar to the military... this is what prevented the other 3 officers from getting involved. It's us vs. them in many of their minds and this isn't something that can easily change.
The police, the government, healthcare, immigration... it all needs to be rebuild to support a 2020 civilization, but instead people hold onto laws and values from the 1700s because it was written on paper by some people the US likes to glorify.