Relatives of a family killed in a fiery chain-reaction crash in western Nebraska are suing the trucker who crashed into them and five other transportation companies for negligence.

The wrongful death lawsuit in U.S. District Court of Nebraska was filed by the parents of Christopher and Diana Schmidt, a Gaithersburg, Md., couple killed in September with their two young children and unborn son. The Schmidts were originally from California and were returning to live in Sacramento.

Authorities say Illinois truck driver Josef Slezak failed to stop for traffic at a standstill on Interstate 80 because of another truck crash. The lawsuit accuses those truckers of negligence, including Keith Johnson, of Big Lake, Minn., who was killed.

Slezak is charged with four counts of manslaughter and five counts of vehicular homicide.