Driver killed in race accident

Veteran NASCAR champion Tony Stewart retreated from competition on Sunday after he struck and killed an aggrieved young driver walking on a dirt track in a low-stakes race, in an incident highlighting the risks and bravado around car racing.

Authorities in New York state said that they had found no evidence of criminal behavior and that Stewart, a tempestuous racer and one of the highest-paid drivers in NASCAR, was cooperating with investigations into Saturday night's death.

Earlier in the day, the 43-year-old Stewart withdrew from Sunday's high-profile NASCAR Sprint Cup Series at Watkins Glen, New York, but only after a storm of criticism on social media when a team official told reporters that Stewart was proceeding with "business as usual." Ontario County Sheriff Philip Povero said no evidence of criminal intent had been found in the death of driver Kevin Ward Jr, 20.

"At this very moment, there are no facts in hand that would substantiate or support a criminal charge, or indicate criminal intent on the part of any individual," Povero told a news conference.

In the low-stakes race at Canandaigua Motorsports Park, about 25 miles (40 km) southeast of Rochester, Stewart appeared to have clipped Ward's car and caused it to spin out of the race, according to videos posted online.

"There aren't words to describe the sadness I feel about the accident that took the life of Kevin Ward Jr," Stewart said in a statement.