If you look at Preet, it says one of his first bosses was Schumer. He could have been removed if Schumer is going to be charged with something sure to conflict of interes/integrity doubts.
Not a detective, but a NY Judge and a highly suspicious death last year.
http://nymag.com/daily/intelligencer/2017/05/nypd-closes-investigation-into-new-york-judges-death.html
They promoted her posthumously.