Based my knowledge of that intersection and from the pictures I've seen of where the limo came to rest, it looks to me like it went through part of the parking lot and in to a wooded ditch area, where it probably hit the side of that ditch, possibly sideways. Of course, it's all speculation now. The NTSB says they expect the investigation to last about 5 days.
If it was in fact that there was a mechanical issue or a driver incapacitation, it happened at a most unfortunate location. They came down 30 from Amsterdam, and there are plenty of places where a car could go off the road at a curve at the bottom of a hill and go into into a corn field or cow pasture and while it wouldn't be great, it would be much more survivable.