"So, I'm just calling because I'm obligated to for this investigation. I'll just need you to swing by my office and sign a form saying I questioned you. We can grab a few beers too, write it off as business expense."

Cops that are willing to hold other cops accountable don't end up having much upward mobility within the ranks. You don't get to a position where you are investigating the police, but being good at investigating the police.

“we investigated ourselves and found no wrongdoing”