NASCAR's Kyle Busch died after severe pneumonia progressed into sepsis, his family says

Kyle Busch died after severe pneumonia progressed into sepsis, resulting in rapid and overwhelming associated complications, according to a statement released by his family.

Dakota Hunter, vice president of Kyle Busch Companies, said in a news release the family received the medical evaluation on Saturday.

Busch, a two-time NASCAR champion, died at 41 on Thursday, a day after passing out in a Chevrolet simulator.

Sepsis is considered a life-threatening medical emergency that occurs when the body has an extreme, overactive response to an infection, causing the immune system to damage its own tissues and organs, according to the Centers for Disease Control and Prevention.

Typically the immune system releases chemicals to fight off pathogens like bacteria, viruses or fungi, but with sepsis the response goes into overdrive. The results can cause widespread inflammation, form microscopic blood clots and make blood vessels leak.

Busch was thought to have had a sinus cold while racing at Watkins Glen on May 10 and radioed in to his team saying that he needed a "shot" from a doctor after the race.

However, he bounced back to win the Trucks Series race at Dover last weekend, and then he finished 17th in the All-Star race on Sunday.

Busch, who was preparing to race Sunday at the Coca-Cola 600 at Charlotte Motor Speedway, was testing in the Chevrolet racing simulator in Concord, N.C., on Wednesday when he became unresponsive and was transported to a hospital in Charlotte, several people familiar with the situation told The Associated Press.

During the emergency call placed late that afternoon, an unidentified caller calmly told the dispatch: "I've got an individual that's [got] shortness of breath, very hot, thinks he's going to