Transfer Case problems of the 2003 Jeep Cherokee

(1) I pulled the Jeep grand Cherokee to a stop in front of a self-serve car wash bay where the previous user had left the car wash wand hanging in the middle of the bay. With my foot on the brake, I opened the driver door and put the vehicle in park; then proceeded to exit the vehicle to move the wand. (I did not turn the ignition off since I was only going about 10 feet to move the wander out of the way. ) while I was standing between the driver's seat and open door, the vehicle started rolling backwards. 2) the failure was the vehicle gear shift slipping from "park" to "reverse", or being in the "park" gear enough to stop the vehicle and allow me to get out, but not "locking" in the "park" gear, and thus slipping back to "reverse". After I was standing outside the vehicle, it started to roll backwards, too fast for me to get inside to apply the brake. The driver's door got caught on a nearby vacuum structure, causing the door to sprain. The back end of the Jeep rolled over a low cement wall which is around the perimeter of the car wash. The center of the vehicle got hung on the wall, causing the vehicle to stop and damage to the transfer case and underbody. (3) nothing has been done to correct the failure at this time. The vehicle will require a new driver's door and front side panel, and a new transfer case. Total damage to vehicle- approx. $5,000.