Yikes, that's horrendous.
Just a guess of course, but my first feeling is the truck carries a lot of the blame. That's the kind of thing that happens when someone loses control of a big vehicle at the wrong time.
As many here know, I drive a lot. I've seen some horrific accidents. It always seems that the worst ones are when a vehicle crosses a lane or the center divider into oncoming traffic. Whether it's a drunk, a blowout or cellphone activity, the result is often like the picture above.
Probably the oddest crash was when a Kia SUV lost a front strut + wheel and tire assembly in the middle lane of I-95, while going more than 80MPH. It rolled horrifically, seemingly forever, but hit nobody. The tire and strut assembly went on a wild path that took out a few cars.