Ward had been walking and pointing toward Stewart's car after Stewart spun out the young driver's sprint car.
"The prior lap, Tony had gotten into him - just spun him, nothing big, just spun him around," a 27-year-old spectator told USA Today. "The caution came out. [Ward] hopped out to go and yell and point a finger at Tony, typical thing. "Tony came around ... the back end slid out, and he definitely caught him ... the body made contact with the car and went sliding across the track a long distance, at least 50 feet. It was the worst thing I've ever seen."
The incident is being treated as an on-track crash and an investigation is ongoing. Ontario County Sheriff Philip Povero told the Associated Press that the investigation is not criminal, adding that Stewart was "fully cooperative" and appeared "very upset" as he was questioned and released.
Here's the video (warning: Graphic):