Trucks have a high center of gravity and are more prone to fill than a car. The car was traveling at a high rate of speed and when it hit truck it probably lifted the truck up as it went under it.
Very tragic and sad. I have a teenager who will get his license in two months and it scares me not knowing what will happen when he driving on his own. All we can do is coach and train our kids to drive responsibly and put the rest in Gods hands.
Make sure you wear you seatbelt, the airbags don't work well without the seatbelts.