Busch died on May 21, just hours after his family announced that he would not be competing in the Coca-Cola 600 that weekend. His cause of death was determined as severe pneumonia, which progressed into sepsis.

"The medical evaluation provided to the Busch Family concluded that severe pneumonia progressed into sepsis, resulting in rapid and overwhelming associated complications," the Busch family shared statement, per NBC News. "The family asks for continued understanding and privacy during this difficult time."

More details had come to light since Busch's death, including him passing out while testing in the Chevrolet racing simulator, several people familiar with the situation told the Associated Press. He was unresponsive and quickly transported to a hospital nearby.

Following his passing, NASCAR paid tribute to Busch, who was one of the most decorated drivers in the sport's history. 

"A future Hall of Famer, Kyle was a rare talent, one who comes along once in a generation," the association wrote on X. "He was fierce, he was passionate, he was immensely skilled and he cared deeply about the sport and fans." 

"NASCAR lost a giant of the sport today, far too soon," NASCAR emphasized in its statement. "During this incredibly difficult time, we ask everyone to respect the family's privacy and continue to keep them in your thoughts and prayers."

For a closer look at Busch's life, keep reading.