Car possessed?

This morning, on going into the garage, noted that the rear end of my car (2014 350 F-Sport AWD), which had been turned off since last night, sounded like a hybrid when you first open the front door (buzzing sound). The sounds came from the rear end. Again, the car had been turned off since last night (7 hours ago). Car started easily, but the sounds were likely on all night.

Theories