Stewart, 43, bumped cars with Kevin Ward Jr. during a sprint car race last Saturday at Canandaigua Motorsports Park in upstate New York. With the yellow caution flag out and Stewart continuing to race, Ward got out of his car and, while in the middle of the track, pointed at the three-time NASCAR champion.
What happened next shocked spectators and has the US racing world asking questions about Stewart's conduct: his car struck the 20-year-old driver, killing him.
The right rear tyre of Stewart's vehicle hit Ward, sucking him under the wheels, before the force of the car threw him down the track. He died of his injuries.
The manner of the fatal incident was horribly ironic given that angrily walking on to a race track is something Stewart himself is famous for having done in the past.
US media outlets have pointed to the "grim irony" that Ward was acting just like Stewart, a fiery driver who has an insatiable thirst to win.
In August 2012, Stewart stormed on to the NASCAR track in Bristol, Tennessee, having been wrecked by Matt Kenseth and threw his helmet at Kenseth's oncoming car, Slate reported.
"I’d like to believe that Stewart, on a Saturday night in Canandaigua, New York, competing in a minor-league race for the love of the sport, would have seen something of himself in Ward," Slate deputy editor John Swansburg wrote.
"I’d also like to believe that Stewart just didn’t see Ward at all, until it was too late."
Flowers lay next to the front entrance of the Canandaigua Motorsports Park (Getty)
Fellow drivers and racing experts have differing views about whether Stewart knew Ward was on the track or not.
The New York Times reported that it was not the first time Stewart crashed at the track. In July last year, Stewart was part of a 15-car pile-up. He apologised for causing the crash and driving too aggressively.
The US newspaper reported Stewart had a reputation for having confrontations with drivers, officials and reporters.
Tyler Graves, a sprint car driver and a friend of Ward, told Sporting News: "I know Tony could see him. I know how you can see out of these cars. When Tony got close to him, he hit the throttle.
"When you hit a throttle on a sprint car, the car sets sideways. It set sideways, the right rear tyre hit Kevin, Kevin was sucked underneath and was stuck under it for a second or two and then it threw him about 50 yards."
Ontario County Sheriff Philip Povero said in a statement: "Investigators continue to seek witnesses, gather evidence, and develop the racetrack crash reconstruction."
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