Xue Sheng
All weight is underside
That's good. It means the crumple zones worked, and absorbed all the kinetic energy that would otherwise have impacted the passengers. That's a big part of why there were no ambulances.
Also there apparently was no one in the back seat, the bumper of that cement mixer went right over it all the way to the back of the front seat
It was one of these types of cement mixers
I think what put a concave in the lower part of the back was the front axle of the cement mixer