Tony Stewart will not compete in Sunday's NASCAR Sprint Cup race in Watkins Glenn, N.Y., after the driver he struck in a dirt-track race Saturday night was killed.

Sprint car driver Kevin Ward Jr., who climbed out of his car on the track to confront Stewart, later died after he was hit by Stewart's car at Canandaigua (N.Y.) Motorsports Park.

Greg Zipadelli, the competition director for Stewart-Haas racing, announced Sunday morning that Stewart will not race in Sunday's Cheez-It 355. He was replaced by Regan Smith.

Zipadelli said it was Stewart's decision to not race after Ward's fatal accident.

"I support Tony Stewart. I think I have shown that over the last 18 years." Zipadelli said.

Zipadelli earlier said Stewart would race, calling it "business as usual." Stewart, a three-time NASCAR champion, is in contention for the Chase this year. Sunday's race is significant for Stewart's championship hopes but he decided to sit it out after taking "some time to sleep on it," Zipadelli said.

"(Stewart) feels strongly this is the right thing to do. We at SHR support it and agree with it. It's a difficult time for both parties. This is what we feel is right and we're supporting Tony in it," Zipadelli said.

Ontario County Sheriff Philip Povero said the department is not conducting a criminal investigation. He said Stewart was "fully cooperative" and "very upset" about Saturday night's incident. Stewart was not injured.

"He was visibly shaken by this accident," Povero said. "... This is right now being investigated as an on-track crash and I don't want to infer that there are criminal charges pending. When the investigation is completed, we will sit down with the district attorney and review it. But I want to make it very clear: there are no criminal charges pending at this time."

A video of the crash at Canandaigua Motorsports Park showed Ward, who was wearing a black helmet and a firesuit on the dimly lit track, walking toward Stewart's car before being struck and thrown about 50 feet.

Ward, 20, was pronounced dead Saturday night at a hospital in Canandaigua.

Povero said Stewart, 43, was questioned and released.

The sheriff's department asked for people with video of the accident to contact the office so it can be reviewed.

"People that witnessed it were horrified," Povero said. "They were extremely shocked."

Video shows Ward, in the No. 13 car, spin into a wall after making contact with Stewart's car. Ward then climbed out of his car and walked by Stewart's No. 14 car to confront him as he passed by. Ward was to the right of Stewart's car, which appeared to kick out from the rear and strike Ward. Then, Ward was thrown through the air.

Canandaigua Motorsports Park canceled the remainder of Saturday's race within five minutes and later posted a message on its Facebook page asking fans to "pray for the entire racing community of fans, drivers, and families."

Stewart was involved in an accident at Canandaigua in July 2013 that seriously injured a 19-year-old driver.

One year and four days ago, Stewart broke his right leg in a sprint car race in Iowa and missed the second half of the season.