WATKINS GLEN, N.Y. -

A spokesman for Tony Stewart calls the death of a fellow driver he struck and killed at an upstate New York dirt track a "tragic accident."

The three-time NASCAR champion hit Kevin Ward Jr. on Saturday night as Ward walked toward Stewart's car following an on-track incident at Canandaigua Motorsports Park.

A video of the crash shows driver Kevin Ward Jr. stepping toward Stewart's car before being hit and hurtled 50 feet. The Ontario County Sheriff's Department would not identify the driver but said he was pronounced dead on arrival Saturday night at a hospital in Canandaigua.

Witnesses say Ward appeared to be trying to confront Stewart when the rear of Stewart's car hit him.

Sheriff Philip Povero says the 42-year-old Stewart was "fully cooperative" as he was questioned and released. Povero says the investigation is not criminal.

In a statement released Sunday morning, a representative for Stewart says, "our thoughts and prayers go out to his family and friends." The statement says Stewart's team is still trying to sort through the details of the accident.

Stewart was scheduled to race later Sunday in NASCAR's Sprint Cup race at Watkins Glen. Greg Zipadelli, competition director for Stewart-Haas Racing, said the three-time NASCAR champion "feels strongly" he should not race at Watkins Glen following Kevin Ward Jr.'s fatal accident.

Regan Smith will replace Stewart in the car.