NASCAR star Tony Stewart said he didn't see a driver walking on a dirt track in upstate New York last year before he struck and killed him, and noted the racer was impaired by marijuana and shouldn't have been outside his car, according to court papers filed Friday.

Kevin Ward Jr.'s family filed a lawsuit this month that accused Stewart of gross negligence, saying he gunned his engine and put his card into a skid as the 20-year-old Ward walked on the track after a crash at Canandaigua Motorsports Park on Aug. 9, 2014.

Stewart's attorney, Brian Gwitt, argued in an answer to the Ward's lawsuit that the racing star didn't see the crash Ward had been involved in and didn't realize anyone was standing on the track.

"Stewart was not aware that anyone had exited their vehicle," Gwitt wrote, adding that his client "did not see Ward, Jr. or anyone else walking on foot on the track until just prior to contact, and did not know the identity of the person walking on the track until afterward."

Gwitt claims Ward's death was caused by his own decision to exit his car and walk along the track while the race was still going on. The court filing says a toxicology report showed Ward had smoked marijuana within five hours of the competition, a violation of the race's rules and regulations, which "impaired him."

Ward's parents, Kevin and Pamela Ward, are seeking unspecified monetary damages, in their suit, which claims wrongful death, reckless conduct, gross negligence and their son's terror and suffering.

The lawsuit notes Stewart's reputation for having a temper and claims that Stewart deliberately veered toward Ward after the collision.

Stewart denied those allegations and his lawyer argued that Stewart had never met Ward before and didn't even know there was a crash before he came up to it, because it happened behind him.

Stewart also claims that Ward's death was "caused in full or in part" by his parents, "who permitted or failed to prevent an impaired driver from participating" in the race.

Evidence from the crash was presented to a grand jury in upstate New York, which declined to indict Stewart and called the incident "100 percent an accident."

An attorney for Ward's family did not immediately respond Friday evening to an email seeking comment.