Sprint car driver Kevin Ward Jr. died on Saturday when Stewart's car hit the 20-year-old as he was walking on the dirt track in Canandaigua, New York, to confront Stewart after his car bumped Ward's.
"Apparently, Tony Stewart was the only one driving out there who didn't see him," Kevin Ward Sr. told the Syracuse Post-Standard on Tuesday.
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Noting that his son had never before left his car during a race, he added, "I think the reason he probably got out of that car is who put him into the wall. He was definitely put into the wall."
Investigators are looking into the possibility that Stewart hit the throttle when he approached Ward.
No charges have been filed against Stewart but the investigation will last at least another two weeks, authorities said.
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