NASCAR driver Tony Stewart's racing team is calling it a "tragic accident." 


The three-time champion struck and killed a Sprint Car driver during a dirt-track race in upstate New York Saturday night.


Witnesses say Kevin Ward, Jr., had climbed from his car and was on the track trying to confront Stewart when the rear of Stewart's car hit him.


Stewart is being investigated for for the incident.


Video shows Ward spin out and exit his car on foot, walking out into the middle of the dirt track race.  


Police say Stewart was cooperative during questioning at the scene. 


Stewart's managers now say he will not drive Sunday in the NASCAR Sprint Cup race at Watkins Glen International Raceway. 









(Photo: Jerry Markland / 2014 Getty Images)