An autopsy report shows that former Clemson running back C.J. Fuller died from a blood clot in his lungs.

On Tuesday, Pickens Country (South Carolina) Coroner Kandy Kelley said in her report that Fuller died from a “Pulmonary thromboembolism and deep vein thrombosis,” according to the Associated Press. The former Clemson running back was just 22 years old.

Thromboembolism is a sudden blockage of the lung and the deep vein thrombosis was caused by the blood clot in his leg.

Fuller injured his knee on Aug. 12 and had surgery on Sept. 19. He died on Oct. 3. According to Kelley, his death is related to that knee injury.

Fuller played for three seasons at Clemson and was a member of the Tigers’ 2016 national championship team.