There are new details on Kyle Busch‘s illness that led to his death. PEOPLE obtained the death certificate, which said that Busch had been battling illnesses for “weeks.” Busch had bacterial pneumonia “of an undetermined etiology” for “days to weeks” before his death.

PEOPLE said that the pneumonia then progressed to sepsis, and within hours, caused disseminated intravascular coagulation. Busch died 24 hours after being rushed to a hospital in Charlotte, North Carolina, on May 21, when his sinus infection progressed into pneumonia and sepsis.

One day before his death, Busch was coughing up blood and lying on the floor of a bathroom after he passed out while on a racing simulator. Audio from the 911 call was released, and the caller described Busch’s condition.

“I’ve got an individual that’s [got] 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,” the caller said. “He is awake. He’s awake on the bathroom floor right now.”

NASCAR CEO reacts to Kyle Busch’s death

NASCAR announced Kyle Busch’s death last Thursday evening, and the news sent shockwaves through the racing community. On Friday, May 22, NASCAR CEO Steve O’Donnell spoke to the media about Busch.

“I’ve spent 31 years in this sport, and Kyle Busch has been part of my life for 25 years,” O’Donnell said. “Watching him come into the sport as a teenager, I think all of us would agree, full of talent, full of fire, didn’t give a damn, was going to push us. I think we all loved that spirit. And over those years, I think everything you saw on the track was one thing, but there was so much more to Kyle Busch that I think it’s important for people, maybe even new to the sport, to understand.

“…Kyle Busch lived just about every chapter of what you can do in NASCAR. What most people saw: Rowdy, fierce, he’s competitive, always good for a great quote. My favorite interview Kyle Busch ever gave — and I wish I could do it every weekend, and I know most of you probably hated it, but everything is great, and he just kept saying it over and over and over again. That’s Kyle.”

Busch was one of the most successful drivers in NASCAR history. Along with winning two NASCAR Cup Series championships, Busch won 63 Cup Series races, 102 O’Reilly Auto Parts Series races, and 69 Truck Series races.