New details in NASCAR legend Kyle Busch’s sudden death. Here’s what we know so far.

According to The Associated Press, NASCAR driver Kyle Busch was testing in a racing simulator on Wednesday when he became unresponsive.

Legendary NASCAR driver Kyle Busch died Thursday at 41, three days before he was set to run the Coca-Cola 600 at Charlotte Motor Speedway.

As Busch’s friends, family and fans mourn his death and pay tribute to his legacy, details remain limited on exactly what happened.

Here’s what we know.

On Wednesday, NASCAR driver Kyle Busch was found unresponsive in a driving simulator in Concord, according to new reporting by The Associated Press. He was transported from there to a hospital in Charlotte, several people familiar with the situation told The Associated Press, giving new insight into the hours before the racing star’s unexpected death.

New details from a 911 call indicate that a caller reported a male needing an ambulance at the GM Charlotte Technical Center on Wednesday afternoon. The caller described the individual as having shortness of breath, feeling very hot, believing he was going to pass out and coughing up blood.

Busch was lying on the bathroom floor inside the complex and the caller told dispatch, “He is awake,” according to audio provided by the Cabarrus County Sheriff’s Office.

The man then gave directions on where emergency responders should go and asked that they turn off any sirens upon arrival.

Earlier in the day on Thursday, his family posted that Busch was hospitalized, undergoing treatment for a “severe illness.”

Just hours later, Busch’s family and NASCAR released a joint statement confirming the 41-year-old had died.

“Our entire NASCAR family is heartbroken by the loss of Kyle Busch. A future Hall of Famer, Kyle was a rare talent, one who comes along once in a generation,” the Busch family, Richard Childress Racing and NASCAR said in a joint statement. “He was fierce, he was passionate, he was immensely skilled and he cared deeply about the sport and fans.”

What was Kyle Busch’s cause of death?

As of Friday morning, an official cause of death hasn’t been released for Kyle Busch, whose death has shocked the professional racing world.

His death comes 11 days after Busch radioed into his crew near the end of a Cup Series race at Watkins Glen asking a doctor to give him a “shot” when he finished the race.

According to the TV broadcast, Busch had been struggling with a sinus cold exacerbated by the intense G-forces and elevation changes at the New York road course.

A few days later on May 15, Busch won the NASCAR Craftsman Truck Series race in Dover. Comments from his post-race interview resurfaced as news of his death spread.

“You take whatever you can get, man,” Busch said. “You never know when the last one is going to be, so cherish them all — trust me.”

Credit: AP Photo/Mark Humphrey
FILE – Kyle Busch waits for the start of a NASCAR Xfinity Series auto race Saturday, June 19, 2021, in Lebanon, Tenn.

Fans, rivals mourn Busch’s death

In the short time since Busch’s death was confirmed, an outpouring of support has welled up for his loved ones from fans who enjoyed watching him race and competitors who met him on the track.

NASCAR legend Jimmie Johnson was one of the first to share his condolences with a post on X.

“Kyle Busch wasn’t just one of the fiercest competitors our sport has ever seen, he was one of the most talented race car drivers I’ve ever shared a track with. We spent years as teammates at Hendrick Motorsports, and even as competitors, there was always a deep respect for what he could do behind the wheel,” Johnson wrote. “Kyle pushed all of us to be better. His passion, intensity, and love for racing were unmatched, and his impact on this sport will be felt forever.”

NASCAR driver Denny Hamlin said, “Absolutely cannot comprehend this news. We just need to think of his family during this time. We love you KB.”

On Friday, NASCAR CEO Steve O’Donnell said at a news conference that Busch “defines what it means to be racer in NASCAR. The fire, the greatness, the heart you rarely saw. The sport was truly lucky to have him. We’re going to do our darn best to support his family and continue his legacy.”

O’Donnell said plans are in the works to honor Busch and his legacy at the Coca-Cola 600 but did not share specifics.

J. Douglas Boles, president of IndyCar, said on social media, “We will light the pylon on Lap 18 of the [Indianapolis] 500 in memory of Kyle Busch!”

Fans also paid tribute to Busch with charitable donations, offering symbolic gestures to a charity he started.

By Thursday evening, the Samantha and Kyle Busch Bundle of Joy Fund — the charity Busch and his wife founded to help couples afford fertility treatments — had received hundreds of new donations.

Donations on the charity’s page bore messages like “In Memory of Kyle Busch,” “In Honor of Kyle Busch” and “In Memory of Rowdy,” submitted by fans from across the country. Many gave exactly $18.08, a nod to the two car numbers Busch carried across his storied career. Busch drove the No. 18 during his championship years at Joe Gibbs Racing and wore the No. 8 for Richard Childress Racing in his final seasons.

Kyle Busch’s cause of death revealed: severe pneumonia, sepsis

Kyle Busch died of pneumonia leading to sepsis, according to a statement provided by the Busch family on Saturday morning.

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

Busch, 41, died on Thursday after a brief illness. On Wednesday, he began suffering a medical emergency at the General Motors Charlotte Technical Center in Concord, North Carolina. An unidentified male at the scene called 911, according to a recording obtained by TMZ, saying Busch was suffering “shortness of breath, very hot, thinks he’s going to pass out and is producing a little bit of blood — coughing up some blood.”

Busch was taken to a Charlotte hospital, per the Associated Press, and on Thursday morning his family and Richard Childress Racing announced he would miss this weekend’s Coca-Cola 600 because of an unspecified “severe illness.” At 5:40 p.m. ET on Thursday afternoon, NASCAR announced publicly that Busch had died, shocking the racing community.

“Our entire NASCAR family is heartbroken by the loss of Kyle Busch,” the Busch family, Richard Childress Racing and NASCAR said in a statement. “A future Hall of Famer, Kyle was a rare talent, one who comes along once in a generation. He was fierce, he was passionate, he was immensely skilled and he cared deeply about the sport and fans. Throughout a career that spanned more than two decades, Kyle set records in national series wins, won championships at NASCAR’s highest level and fostered the next generation of drivers as an owner in the Truck Series. His sharp wit and competitive spirit sparked a deep emotional connection with race fans of every age, creating the proud and loyal ‘Rowdy Nation.’”

Twelve days prior to his death, Busch had complained of sinus issues while racing at Watkins Glen and asked for a doctor to visit him in his hauler after the race. However, he continued to race afterward, even winning a Truck Series race in Dover, Delaware, one week ago.

The winningest driver in history across all of NASCAR’s three national series, Busch won two Cup series championships and 234 races in his career. A team owner as well as driver, he made his mark on the sport of NASCAR in innumerable ways and had been training son Brexton to follow in his footsteps. Busch was in the midst of his 22nd Cup season, driving for Richard Childress Racing.

Busch is survived by his wife, Samantha, children Brexton and Lennix, brother Kurt and many other family members.

NASCAR will be running the Coca-Cola 600 as scheduled this weekend. Austin Hill will be driving Busch’s car.