Too much power?

After learning about these events all I could think about was did all theses events have to end the way they did, and what caused police to do the things they did. Personally I feel it was misuse of their power. In two of these events these cops most likely thought I can get away with this as long as I report it was self-defense. With the events that occurred police should be required to take some kind of test or program that requires officers to be qualified enough to not misuse their power.