Do you think police officers get too comfortable? (details inside)

I was driving to an appointment today and I came to a red light. I stopped, and on the opposite side was a police officer, who immediately did a U-turn in the intersection (driving over 2 curbs in the meanwhile) and then sped in the opposite direction without his lights or sirens on.
I can only suspect that there was a reason he felt the need to do this, but without his lights or sirens seems a little bit dangerous. It isn’t the first time I’ve witnessed such a thing, either. I used to drive out into the country frequently and I saw it all the time there. If I pulled up to a red light or a 4 way stop, police officers would always turn on their lights and pull through, then shut their lights right off.

Have you seen similar situations? Why do they do that? Is it an abuse of power, are they just too comfortable in their jobs and they forget the little details, or is there some kind of protocol that I don’t know about involving traffic jams and stop lights?