Kyle Busch's cause of death released by family

Kyle Busch's family has released more information on the NASCAR champion's shocking death. 

Busch died Thursday at age 41. 

Kyle Busch cause of death

What they're saying:

According to FOX Sports reporter Bob Pockrass, Busch's family released the following statement on his cause of death: 

"The medical evaluation provided to the Busch Family concluded that severe pneumonia progressed into sepsis, resulting in rapid and overwhelming associated complications."

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Busch thought he had a cold while racing at Watkins Glen on May 10 and told his team he needed a "shot" from a doctor after the race.

He was testing in the Chevrolet racing simulator in Concord, North Carolina, on Wednesday when he became unresponsive and was taken to a hospital in Charlotte. 

Busch, who was preparing to race Sunday at the Coca-Cola 600 at Charlotte Motor Speedway, experienced shortness of breath, felt he was overheating and was coughing up blood, according to a 911 call obtained by the AP.

What is sepsis?

According to the U.S. Centers for Disease Control and Prevention, sepsis is an extreme, overactive response to an infection that causes the immune system to damage its own tissues and organs. Most people will recover from mild sepsis, according to the Mayo Clinic, but the mortality rate for septic shock is 30% to 40%. 

Kyle Busch's legacy

The backstory:

Busch is described as arguably the greatest driver of his generation, notching a combined 234 wins — 63 in the top-tier Cup Series and another 171 in NASCAR’s two feeder series, O’Reilly (102) and Trucks (69). In his 26-year career, Busch had a lot of nicknames – Wild Thing, Outlaw, Rowdy and KFB to name a few – all of which were in line with his reputation for bucking the system. 

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"Kyle Busch just defines what it means to be a racer in NASCAR, everything about it, the fire, the greatness, the heart that sometimes you rarely saw," NASCAR CEO Steve O'Donnell said Friday. "The sport was truly lucky to have him. And I believe I can speak for everybody in the sport … We're gonna do our damn best to continue his legacy and support his family."

All 39 drivers in the field for Sunday’s Coca-Cola 600 race will race with a black No. 8 decal on their car to honor Busch.

NASCAR