Chicago Bears legend Dick Butkus died from a “cerebrovascular accident,” or stroke, according to his death certificate.
The Hall of Fame linebacker also suffered from atrial fibrillation – an irregular heartbeat, high cholesterol and atherosclerosis – clogging of the body’s arteries, People reported.
Butkus died on Oct. 5 at age 80.
Butkus also underwent coronary bypass surgery in 2001, according to the death certificate.
The linebacker was a first-ballot Pro Football Hall of Fame inductee, an eight-time Pro Bowler, a five-time All-Pro, and a member of two All-Decade teams.
In 2019, Butkus was named to the NFL’s 100th Anniversary All-Time Team.
Butkus was known as one of the most feared players in the game’s history.
“If I had a choice, I’d sooner go one-on-one with a grizzly bear,” Green Bay Packers running back MacArthur Lane said, via the Bears’ website after Butkus’ death. “I pray that I can get up after every time Butkus hits me.”