John Feinstein — a longtime sports reporter and author — has died at the age of 69 … according to his employer, the Washington Post.

John’s brother — Robert — confirmed his passing to the outlet on Thursday. His cause of death was not revealed.

Feinstein started his career at the Post in 1977 … working as a night police reporter before joining the sports beat. He was the author of 48 books, 23 of which became a New York Times best seller. One of his most well-known pieces was “A Season on the Brink,” which followed the 1985-86 Indiana University men’s basketball team led by Bob Knight.

He had a column published Thursday morning by the Post … which was about Michigan State head coach Tom Izzo.

Many media members, along with readers of his work, have taken to social media to comment on his passing.

He was 69.