High Pitch wine under dash immediately when car is turned off on 2005 Cadillac Escalade

I just sat through stop and go traffic of the first snow storm of the year. My engine temp did get hot (half way to the top), which for this rig isn't serious and it sat there for a couple hours for my long trip home. I pulled in to my garage, turned off the car, and before I could pull the keys out a shreaking sound caught my attention. It only lasted for a couple second. I immediately turned the car back on, let it idle, turned it off and heard nothing.

Asked by for the 2005 Cadillac Escalade