The sports world is grieving on Sunday after the passing of Boston Celtics legend and civil rights icon Bill Russell.

Paul Pierce, Finals MVP for the Celtics' last championship in 2008, paid emotional tribute to his mentor and friend on social media, lavishing Russell with praise and remembering a day he and Kevin Garnett listened to Russell's stories like “kids sitting around a campfire.”

Pierce was drafted No. 10 overall by the Celtics in 1998, spending the first 15 seasons of his career in Boston. He quickly enjoyed individual success in the league, establishing himself as one of basketball's best young wings alongside the likes of Kobe Bryant, Tracy McGrady and Vince Carter. But team glory eluded the Celtics during Pierce's tenure until they traded for Kevin Garnett in summer 2007, establishing a new Big Three with Ray Allen.

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Russell was on the court at TD Garden the following June, embracing Pierce, Garnett and the Celtics after they beat the rival Los Angeles Lakers in Game 6 of the NBA Finals, winning the franchise's first title since 1986.

The most decorated player in NBA history, Russell won a remarkable 11 championships with the Celtics, including eight straight from 1959 to 1966 and two more as player-coach in 1968 and 1969. He and Pierce were inducted together to the Naismith Memorial Basketball Hall of Fame last year, making Russell the fifth person ever to receive the honor as both a player and coach.

Russell passed away peacefully on Sunday. In a statement, his family encouraged mourners to “relive one or two of the golden moments he gave us, or recall his trademark laugh”—advice an emotional Pierce is already heeding.