CONCORD, N.C. (AP) — NASCAR driver Kyle Busch died Thursday at 41, three days before he was set to run the Coca-Cola 600 at Charlotte Motor Speedway.

Here is what to know:

How did Kyle Busch die?

At this point, the cause of death has not been released and details remain limited.

What is known is that Busch was testing in the Chevrolet racing simulator in Concord on Wednesday when he became unresponsive and was transported to a hospital in Charlotte, several people familiar with the situation told The Associated Press on condition of anonymity because details have not been disclosed by Busch’s team or family.

Had Kyle Busch been ill?

Busch was thought to have had a sinus cold While racing May 10 at Watkins Glen, Busch radioed his team requesting a “shot” from a doctor after he finished. Per the TV broadcast, Busch had been struggling with a sinus cold that was exacerbated by the intense G-forces and elevation changes at the New York road course.

It’s unclear if that issue had something to do with his death.

Busch did race last weekend and won the Trucks Series race at Dover and finished 17th in the NASCAR All-Star race. That would be his final race.

How good was Kyle Busch?

Busch won 234 races across NASCAR’s three national series — more than any driver in history. He won Cup season championships in 2015 and 2019 for Joe Gibbs Racing.

His first championship was particularly impressive. Busch missed the first 11 Cup races of the 2015 season after injuring his foot following a crash in the O’Reilly Auto Parts series opener in Daytona, but came back to win five races to qualify for the playoffs before capturing the title at Homestead.

Will the Coca-Cola 600 be postponed or canceled?

No. NASCAR officials confirmed that the 400-lap race will continue on as planned Sunday night at the 1 1/2-mile track at Charlotte Motor Speedway.

Earlier in the day, RCR had announced that Austin Hill would replace Busch in the No. 8 Chevrolet Camaro ZL1.

Does CMS plan to honor Kyle Busch?

Yes, CMS officials said they plan to honor Busch “in some way” this weekend at the Coca-Cola 600, but details were still being ironed out.

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AP freelance writer and former AP auto racing writer Jenna Fryer in Indianapolis contributed to this report.

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AP auto racing: https://apnews.com/hub/auto-racing