NASCAR star Kyle Busch became unresponsive while testing a racing simulator in Concord, N.C., the day before his death and had to be hospitalized, sources told the Associated Press.

Busch died Thursday at the age of 41 after being hospitalized with what had been described as serious illness, and no official cause of death has been revealed.

His family posted a message on his X account on Thursday at 10:23 a.m. ET stating he had been hospitalized and would not compete this weekend.

“Kyle has experienced a severe illness resulting in hospitalization,” the family wrote. “He is currently undergoing treatment and will not compete in any of his scheduled activities this weekend at Charlotte Motor Speedway. We ask for understanding and privacy as our family navigates this situation.”

Busch’s family, Nascar and Richard Childress Racing then released a statement a little over seven hours later announcing he had died.

“A future Hall of Famer, Kyle was a rare talent, one who comes along once in a generation,” the joint statement read. “He was fierce, he was passionate, he was immensely skilled, and he cared deeply about the sport and fans. Throughout a career that spanned more than two decades, Kyle set records in national series wins, won championships at NASCAR’s highest level and fostered the next generation of drivers as an owner in the Truck Series. His sharp wit and competitive spirit sparked a deep emotional connection with race fans of every age, creating the proud and loyal ‘Rowdy Nation.’”

Busch dealt with a medical issue earlier this month, with the star racer saying during the middle of a May 10 race that he would need to see a doctor after finishing his circuit.

The broadcast crew mentioned that he had been dealing with a sinus issue, with the AP reporting that the broadcasters noted how “Busch had been struggling with a sinus cold exacerbated by the intense G-forces and elevation changes at the New York road course.”

“I’m gonna need a shot,” Busch said during the race.

The ailment still bothered him last week, when he told The Athletic while motioning toward his face: “You can kind of hear it, I’m still not great. The cough was pretty substantial last week.”

Busch was one of NASCAR’s greatest drivers, twice winning the Cup Series (2015, 2019) and ranking ninth all-time in NASCAR Cup Series wins with 63.

His final race came Sunday at the Nascar All-Star Race, where he finished 17th.

Busch is survived by his wife, Samantha, 11-year-old son Brexton and 4-year-old daughter Lennix.