Here is the explanation folks.
First off the cops are drinking buddies with the FedEx guy. They're standing around around waiting for this singing telegram dork with the sewing machine to go and deliver his singing telegram about how some sexy asian chick sewed some dudes heart back together after she broke it. Unfortunately the guy paying for this dude to sing to his chick is going to have his heart broken once again because his sexy asian chick is going to hump this guys brains out when she sees a dude in a tuxedo with a sewing machine. That's secret code for hump my head off amidst asian chick circles. So when this guy leaves to get his head humped off, the cops and the fed ex dude are going to ghost ride this fed ex truck (which funny enough happens to have some a few bass combo amps packed with children's inflatable o-rings in the back) backwards down this hill. They'll take bets on who can get it to land standing up first. My money goes on the fed ex driver simply because he's got more experience than the other guys at driving this thing. However, the cops can drink him under the table.