The problem with police is that a lot of the kinds of people who are attracted to the idea of a career wearing a uniform, a badge, and a gun -- and all the authority that goes along with it -- are assholes. "I would like a career where I get to handcuff people and throw them in jail" comes from (1) an overbearing hero fantasy and / or (2) narcissism with sado-masochistic overtones. Not saying all cops are like this, but that it's a profession that these types of people naturally find appealing.
Police are necessary, though, so the way a free society is supposed to manage the risk of abuse of power is through training and accountability. The fact that we don't really have a credible story -- or much of a story at all, really -- from the police department speaks volumes.