Engine probably running, and since it's Ground/HD, the parking brake was probably inoperative (too costly to fix) Those look like some friendly dogs. Official FedEx policy is to throw your body under the wheels to minimize liability for the company...a human chock.
This is an "independent contractors" van. The driver probably rented it, but FEDEX has no reason to train these people cause they are independent of FEDEX. "WINK"
Its a "home delivery" van and these guys come and go. Mostly go.
Allthough watching it is hilarious, this driver is lucky the van split the tree and the house or it would have run straight into the home causing serious damage.