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Bill Russell, one of the greatest basketball players of all time who led the charge on and off the court, has died, his family announced Sunday. He was 88.

Russell’s family said in a statement that he passed away "peacefully" with his wife by his side. It was unclear how Russell died. 

"It is with a very heavy heart we would like to pass along to all of Bill’s friends, fans & followers," the statement started.

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Bill Russell watches a game

Former Boston Celtics players Bill Russell, left, and Tom Heinsohn watch the game between the Celtics and the Atlanta Hawks in Game 6 of the Eastern Conference quarterfinals, April 28, 2016, at TD Garden in Boston, Massachusetts. (Brian Babineau/NBAE via Getty Images)

"Bill Russell, the most prolific winner in American sports history, passed away peacefully today at age 88, with his wife, Jeannie, 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."

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Bill Russell at the TD Garden

A member of the Boston Celtics 1966 championship team, Bill Russell is honored at halftime of the game between the Celtics and the Miami Heat at TD Garden, April 13, 2016, in Boston, Massachusetts. (Mike Lawrie/Getty Images)

His family said that while his wins on the court were one thing, his accomplishments and his fight in the civil rights movement should also be remembered.

"But for all the winning, Bill’s understanding of the struggle is what illuminated his life," the statement read. "From boycotting a 1961 exhibition game to unmask too-long-tolerated discrimination, to leading Mississippi’s first integrated basketball camp in the combustible wake of Medgar [Evers'] assassination, to decades of activism recognized by his receipt of the Presidential Medal of Freedom in 2010, Bill called out injustice with an unforgiving candor that he intended would disrupt the status quo, and with a powerful example that, though never his humble intention, will forever inspire teamwork, selflessness and thoughtful change.

Bill Russell as a Boston Celtics player

Bill Russell of the Boston Celtics poses for a photo circa 1962 at the Boston Garden in Boston, Massachusetts. (Dick Raphael/NBAE via Getty Images)

"Bill’s wife, Jeannie, and his many friends and family thank you for keeping Bill in your prayers. Perhaps you’ll [relive] one or two 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."

NBA Commissioner Adam Silver released a statement after word of Russell’s death came out.

"Bill Russell was the greatest champion in all of team sports. The countless accolades that he earned for his storied career with the Boston Celtics – including a record 11 championships and five MVP awards – only begin to tell the story of Bill’s immense impact on our league and broader society," Silver aid.

"Bill stood for something much bigger than sports: the values of equality, respect and inclusion he stamped into the DNA of our league. At the height of his athletic career, Bill advocated vigorously for civil rights and social justice, a legacy he passed down to generations of NBA players who followed in his footsteps. Through the taunts, threats and unthinkable adversity, Bill rose above it all and remained true to his belief that everyone deserved to be treated with dignity."

Silver added that Russell "was the ultimate winner and consummate teammate, and his influence [on] the NBA will be felt forever."

Bill Russell against the Hawks

Boston Celtics Bill Russell (6) rebounds vs. the St. Louis Hawks at Boston Garden in Boston, Massachusetts. (Richard Meek /Sports Illustrated via Getty Images)

Russell was the No. 2 overall pick of the St. Louis Hawks in the 1956 draft. He was picked behind Si Green, who was chosen by the Rochester Royals, and in front of Jim Paxson Sr., who was selected by the Minneapolis Lakers. Russell would go on to score more points than both players combined.

At San Francisco, Russell helped the Dons win two consecutive NCAA titles in 1955 and 1956. He also led Team USA to a gold medal at the 1956 Olympics.

Russell was traded to the Hawks on draft day for Cliff Hagan and Ed Macauley. He would continue his dominance in the pros, leading Boston to 11 championships, including a run of eight straight. He led the NBA in rebounds five times and is only one of two players to record at least 50 rebounds in a game.

Russell broke the coaching color barrier when he became the first Black NBA head coach in history in 1966. He coached Boston to two NBA championships. He would later coach the Seattle SuperSonics and Sacramento Kings.

Off the court, Russell was a significant leader in the fight for equality as he battled racist abuse, and was public about what he saw and heard while he played.

He and other Black teammates boycotted an exhibition game in Kentucky in 1961 after they were refused service at a restaurant. Russell also supported Muhammad Ali’s refusal to be drafted during the Vietnam War.

Russell was inducted into the Basketball Hall of Fame twice — once as a player and another time as a coach. His No. 6 is retired by the Celtics, and he is the namesake for the NBA Finals MVP award.

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During his illustrious career, Russell was a 12-time All-star, 11-time NBA champion, five-time MVP and an 11-time All-NBA selection.