NASCAR driver Kyle Busch had bacterial pneumonia for “days to weeks” before he died last week at 41, according to a copy of the death certificate obtained by The Athletic on Wednesday.Busch’s pneumonia progressed into sepsis, which lasted one day, per the certificate, which listed the pneumonia and sepsis among a “chain of events” that caused Busch’s death. The sepsis led to disseminated intravascular coagulation (DIC), which causes abnormal clotting throughout blood vessels in the body. That ultimately led to hemorrhagic shock, which is caused by severe internal or external bleeding. The DIC and hemorrhagic shock lasted hours, the certificate said.Busch’s family announced Saturday that the driver had pneumonia that progressed into sepsis, “resulting in rapid and overwhelming associated complications.”The death certificate also noted “cremation” in Mooresville, N.C., as the method of disposition. It noted that he died of natural causes at 4:37 p.m. on May 21.NASCAR, Busch’s family and his race team announced his passing roughly an hour later in a joint statement.“Kyle was a rare talent, one who comes along once in a generation,” their statement said. “He was fierce, he was passionate, he was immensely skilled, and he cared deeply about the sport and fans.”Busch continued to race — and win — while dealing with an illness in the weeks leading up to his death. On May 10, he requested that Bill Heisel, a sports physician assistant who has long worked with NASCAR teams and drivers, meet him in his motorhome following a race at Watkins Glen International, in which he finished eighth. “I’m gonna need a shot,” Busch said over his radio. (Heisel did not respond to messages seeking comment.)The Athletic asked Busch on May 16, a day after his Truck Series race win at Dover Motor Speedway, whether he was feeling better. In response, he motioned to his face and said, “You can kind of hear it — I’m still not great. But the cough was pretty substantial last week.”In the days leading up to his death, Busch attended the opening of an indoor karting facility in Durham, N.C., on May 19, and he posed for photos with fans at his team’s race shop on May 20.However, by that evening, his health seemed to decline quickly. Around 5:30 p.m. on May 20, an unidentified caller requested that an ambulance be sent to the GM Charlotte Technical Center in Concord, N.C., according to 911 audio obtained by The Athletic and other outlets requesting recordings related to Busch last week. The driver was at the racing simulator at the facility the same day, a source briefed on the situation previously said.The caller told the dispatcher that the individual, whose name was redacted in the released audio, was having shortness of breath, feeling very hot, thinking he was going to pass out and coughing up blood. The caller said the individual was awake on a bathroom floor, and asked that responders turn their ambulance sirens off when arriving.NASCAR’s recently completed race weekend at Charlotte saw a multitude of tributes paid to Busch that emphasized the impact he had on NASCAR over his two-plus decades in the sport and why he won’t be forgotten.Among the ways NASCAR honored the fallen champion, most notably, was with a memorial service prior to the Coca-Cola 600, one of NASCAR’s crown jewel races. This included the first public appearance since his death of Busch’s wife, Samantha, and their two children: Brexton, who celebrated his 11th birthday last week with his family, and 4-year-old Lennix.Busch’s parents, his older brother Kurt, nearly every driver in that night’s race, and several team personnel and members of the NASCAR industry also attended. NASCAR CEO Steve O’Donnell spoke eloquently about Kyle and pledged NASCAR would always support the family.