Kyle Busch Died After Pneumonia Progressed to Sepsis, Family Says

Two-time NASCAR Cup Series champion Kyle Busch died from severe pneumonia that progressed into sepsis, his family announced Saturday, bringing clarity to the sudden loss of one of the sport’s most accomplished drivers.

Busch, 41, died Thursday after being hospitalized earlier that week. According to a statement released by his family, a medical evaluation showed that severe pneumonia “progressed into sepsis, resulting in rapid and overwhelming associated complications.” Sepsis is a life-threatening condition that occurs when the body’s response to an infection triggers a chain reaction throughout the body.

The circumstances leading to Busch’s hospitalization unfolded Wednesday afternoon at the GM Charlotte Technical Center in Concord, North Carolina, where the driver was testing in a Chevrolet racing simulator. Emergency calls reported that Busch was coughing up blood, experiencing shortness of breath, and had a high temperature. He was transported to a hospital in Charlotte, where he died the following day.

Busch had shown signs of illness about two weeks before his death, telling his crew chief during a Cup Series race at Watkins Glen that he was not feeling well and requesting...