A fan of some sort is running even after the car is turned off? on 2000 Ford Expedition

I heard a louder humming while driving down the road. After I turned the car off, it continued. It has been running for about 20 minutes. I have not idea what it could be and there is no where to take it to be checked out. When I lifted the hood, it was louder. Do you know what it could be?

Asked by for the 2000 Ford Expedition
It sounds like your radiator cooling fan relay is stuck on. Most likely need a new relay, not uncommon.