I don't feel up to tracking down the URL for the video and newstory but I will give you the jest of it.

The vehicle filming is an 18 wheeler run by Schneider National.

The truck that wrecked lost control due to heavy breaking causing the contents of the trailer to shift. The truck then rolled over the guard railing and tumbled down the hill killing the driver.

It was later discovered after an investigating trooper reviewed the drivers log book that the man killed was a team driver and upon returning to the scene of the accident they found the body of his partner further down the hill in some brush. It was believed that the 2nd man had been asleep in the back of the cab when the accident occurred and had been thrown from the wreckage.