Updated at 10:25 a.m. ET.
In a tragic collision, NASCAR driver Tony Stewart hit and killed fellow driver Kevin Ward Jr., who was walking on a racetrack in upstate New York on Saturday night, authorities said.
Ontario County Sheriff Philip Povero said Ward was dead on arrival at an area hospital, Fox Sports reported.
According to The Associated Press, Povero is not treating the investigation as criminal and Stewart is "fully cooperative" and appeared "very upset" over the incident.
Stewart's team spokesman called the death a "tragic accident." Stewart, 43, was questioned and released, according to Povero.
"Our thoughts and prayers go out to his family and friends," the spokesman said in a statement. "We're still attempting to sort through all the details."
The AP goes on:
"A video of the crash at Canandaigua Motorsports Park showed driver [Ward], clad in a black helmet and firesuit on a dimly lit track, walking toward Stewart's car before being hit and hurtled 50 feet.
"A witness said it appeared Ward was trying to confront Stewart, the three-time NASCAR Sprint Cup Champion. The video showed Ward standing to the right of Stewart's familiar No. 14 car, which seemed to kick out from the rear and hit him.
" 'The next thing I could see, I didn't see (the other driver) anymore,' witness Michael Messerly said. 'It just seemed like he was suddenly gone.' "
The video can be seen here. A warning: the contents are graphic.
Spectators also told Bob Pockrass of Sporting News that the two seemed to have an altercation before the incident. Ward, who had hit the wall and got out of his car, gestured angrily at Stewart. Stewart appeared to hit the throttle before swerving into Ward, witnesses said.
Tyler Graves, another driver and a friend of Ward's who was in the stands at the time, told Sporting News that he did not believe that Stewart intended to hit Ward.
The Associated Press quotes Stewart's racing team manager, Greg Zipadelli, as saying Stewart will race in NASCAR's event Sunday at Watkins Glen, calling the race "business as usual." [Updated at 10:25 a.m. ET: The team appears to have reversed its decision — AP now quotes Stewart's team as saying he won't race on Sunday.]
In any case, the "business as usual" remark didn't sit well with many race fans, many suggesting that, at best, it was insensitive.