Kyle Busch battled illness for 'weeks' according to death certificate

NASCAR star Kyle Busch was potentially ill for "weeks" leading up to his untimely passing, his death certificate revealed Thursday.

The cause of death was confirmed to be triggered by sepsis, which developed from a bout of bacterial pneumonia, as family revealed following Busch's death on May 21. Sepsis triggered clotting within blood vessels that cut off flow to vital organs.

Busch, a two-time NASCAR Cup Series champion who is considered one of the best drivers of all time, was 41.

Busch experienced shortness of breath and was coughing up blood the day before his death, according to a 911 call obtained by USA Today.

He is survived by his wife Samantha, 11-year-old son Brexton and 4-year-old daughter Lennix. He was the younger brother of NASCAR Hall of Fame member Kurt Busch, 47.

The Busch family was on hand for Saturday's Cup Series race at Charlotte, N.C., as NASCAR conducted a weekend of tributes to the late champion.

Those tributes will be ongoing, with rival driver Ricky Stenhouse Jr. revealing he will compete in the O'Reilly Auto Parts Series race at Nashville this weekend with the same NOS Energy Drink paint scheme Busch used until 2017. Busch delivered 22 of his record 102 O'Reilly Auto Parts Series victories with the paint scheme.

Busch accrued a record 234 wins across NASCAR's top three series: 63 in the Cup Series, 102 in the O'Reilly Auto Parts Series and 69 in the Craftsman Truck Series. He won a trucks race at Dover, Del., just six days before his death.

The Las Vegas native was the NASCAR Cup Series champion in 2015 and 2019. He never won the Daytona 500 but claimed the pole for the first time this year before finishing 15th. His biggest wins included the 2008 Southern 500, the 2015 and 2016 Brickyard 400 and 2019 Coca-Cola 600.

--Field Level Media