Authorities said it hadn't been determined whether the explosion was related to terrorism or was simply the suicide of a troubled man.
The victims were in a van that collided with the bus on a northwestern Arizona highway.
A SEPTA bus collided with a Jeep as it pulled out of a driveway in Yeadon, Pa., and the Jeep then struck the tractor-trailer, authorities said.
A computerized brain training program cut the risk of dementia among healthy people by 48 percent.
Dallas Fire Rescue said the child was found in the vehicle and was later confirmed to have died.