NBA legend Bill Russell, an 11-time NBA champion with the Boston Celtics and the first Black head coach in the league, passed away "peacefully" Sunday, according to a family statement from his verified Twitter account. He was 88.

"It is with a very heavy heart we would like to pass along to all of Bill's friends, fans, & followers," the statement reads. "Bill Russell, the most prolific winner in American sports history, passed away peacefully today at age 88, with his wife, Jeannine, by his side. Arrangements for his memorial service will be announced soon.

Bill's two state championships in high school offered a glimmer of the incomparable run of pure team accomplishment to come: twice an NCAA champion; captain of a gold-medal-winning US Olympic team; 11 times an NBA champion; and at the helm for two NBA championships as the first black head coach of any North American professional sports team.

"Along the way, Bill earned a string of individual awards that stands unprecedented as it went unmentioned by him. In 2009, the award for the NBA Finals most valuable player was renamed after two- time Hall of Famer as the 'Bill Russell NBA Finals Most Valuable Player Award.'

Bill's wife, Jeannine, and his many friends and family thank you for keeping Bill in your prayers. Perhaps you'll relive one or two of the golden moments he gave us, or recall his trademark laugh as he delighted in explaining the real story behind how those moments unfolded. And we hope each of us can find a new way to act or speak up with Bill's uncompromising, dignified and always constructive commitment to principle. That would be one last, and lasting, win for our beloved #6

Russell won 11 championships with the Celtics, including eight straight from 1959 to 1966. He was a five-time NBA MVP and a 12-time All-Star.

As a coach for the Celtics, he led Boston to two titles, becoming the first Black head coach to win an NBA championship.

The Celtics issued a statement lauding Russell and his contribution to both the team and the sport as a whole.