You need not go further than the police state that was New Orleans post-Katrina for examples of rogue cops from all across the country wantonly violating the rights of US citizens.
What is now? Fifteen such cops have been successfully prosecuted for murder?
That statistic begs the question of how many more SHOULD BE?
I may be wrong on this, but I know of none that were successfully prosecuted for murder. They were prosecuted for things like "violation of oath of office" or violating civil rights. such things carry a lesser sentence than murder.