The parents of a sprint car driver struck and killed last year by Tony Stewart believe a wrongful death lawsuit is the only way to hold the NASCAR star accountable.

Pamela and Kevin Ward Sr. said Friday on "Good Morning America" they want "justice" for their 20-year-old son.

Kevin Ward Jr. was killed last August at Canandaigua (N.Y.) Motorsports Park when he exited his car under caution in an apparent attempt to confront Stewart. As Ward Jr. walked down the track, he was struck by Stewart's car.

His parents said Friday they don't believe Stewart intentionally struck Ward Jr., but Pamela Ward believes Stewart lost his temper. They also believe Stewart revved his engine and swerved toward Ward Jr.