For days, fans around the world struggled to make sense of the fact that NASCAR legend Kyle Busch was gone. What made the loss even harder was the uncertainty around it. At first, all his family shared was that he had been hospitalized with a “severe illness”. But the seriousness of what was unfolding behind the scenes became clear through a chilling 911 call from the GM Technical Center in Concord, made just hours before NASCAR lost one of its biggest stars. And now, Busch’s family has finally managed to come forward with the official medical explanation behind the sudden tragedy.

“The medical evaluation provided to the Busch Family concluded that severe pneumonia progressed into sepsis, resulting in rapid and overwhelming associated complications. The Family asks for continued understanding and privacy during this difficult time,” the statement read.

“I’ve got an individual that’s shortness of breath, very hot, thinks he’s going to pass out, and he’s producing a little bit of blood, coughing up some blood,” an unidentified caller told dispatch during the emergency call. The caller also said Busch was lying on the bathroom floor inside the complex but was awake, while giving responders directions to reach him. NASCAR CEO Steve O’Donnell later said Busch had been on a simulator at the facility that day.

And now that the family has confirmed that severe pneumonia developed into sepsis, a number of incidents from the previous few weeks seem much more concerning in hindsight.

During the Cup Series race weekend at Watkins Glen, Busch radioed his team asking for medical help immediately after the race, saying he needed “a shot.” Later, Kyle Busch was mentioned by FOX announcers as having what seemed to be a severe sinus illness. Busch persevered through the race and finished in the top ten despite clearly having physical difficulties.

Then Dover arrived. Busch returned to the wheel just days later and produced what would turn out to be the final victory of his illustrious career, winning the NASCAR Craftsman Truck Series race. He also competed in the All-Star Race that Sunday, finishing 17th, which made the speed of what followed even more difficult for the garage to process.

According to the Centers for Disease Control and Prevention, sepsis is considered the body’s extreme and life-threatening response to infection. According to the organization, if treatment is not given swiftly, an infection can soon result in organ failure and death as it spreads and sets off a chain reaction throughout the body. In sepsis, the immune response can go into overdrive, damaging the body’s own tissues and organs instead of only fighting the infection.

The tributes for Kyle Busch have continued pouring in from every corner of motorsports following the shocking loss of the two-time NASCAR Cup Series champion. Drivers, including Dale Earnhardt Jr. and Denny Hamlin, were among the first major figures to publicly honor Busch on Thursday, but the remembrance efforts are now stretching far beyond that.

NASCAR and IndyCar unite to honor Kyle Busch

n a joint statement, the Busch family, Richard Childress Racing, and NASCAR remembered him as “a rare talent, one who comes along once in a generation.” The statement added, “He was fierce, he was passionate, he was immensely skilled and he cared deeply about the sport and fans.”

Denny Hamlin had recently described Busch as “the most talented race car driver” he had ever faced. Brad Keselowski also admitted he knew Busch had not been feeling well, though he did not want to go into specifics. “But then when he ran the Truck race last week, those [thoughts] were honestly kind of erased in my mind,” Keselowski said.

Keselowski also spoke about the pressure drivers often feel to push through pain or illness. “There’s no shortage of drivers that would love to take my seat or anybody else’s seat if we weren’t feeling well, and I think every driver feels that pressure,” he said. “All athletes do. It’s not unique to NASCAR in that sense. We’re all thinking to ourselves, ‘I don’t wanna be replaced.’ … So you try to power through it the best you can.”

Chase Briscoe said Busch’s death served as a “wake-up call” for drivers who often put their health aside while moving from race to race. His message was simple: if something feels wrong, “you need to get checked out.”

Ryan Blaney summed up why Busch remained such a constant presence in the sport, saying, “He was a polarizing figure that no matter if you like him or disliked him as a racer, he was always talked about.” Blaney added that Busch’s personality and competitiveness made him “a larger-than-life person in racing.”

Furthermore, before celebrating Carb Day, officials at Indianapolis Motor Speedway observed a moment of silence. The renowned scoring pylon will illuminate on Lap 18 of the Indianapolis 500 in honor of Busch, according to Speedway President J. Douglas Boles. Given Busch’s past at Indianapolis, the gesture carries more passion. He had recently publicly expressed his desire to compete in the Indianapolis 500 in the future and had won several times on Brickyard 400 weekends.