UPDATE 8/10 10:40a: Tony Stewart will not race Sunday's NASCAR Sprint Cup race at Watkins Glen after striking and killing another driver at a dirt track in Canandaigua Saturday night.

ORIGINAL STORY: NASCAR driver Tony Stewart is being investigated for hitting and killing a fellow driver who walked out onto the track during a race in New York last night. 

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

There are reports he was attempting to confront Stewart, who had just hit Ward's car and caused the spin out.  That's when Stewart struck ward.

Police are investigating the incident and say Stewart was cooperative during questioning at the scene.