A photo showing former NBA great Bill Russell kneeling with his Presidential Medal of Freedom around his neck was posted Monday on social media, an apparent sign the Basketball Hall of Famer supports protesters who are kneeling during the national anthem.

The photo was posted on the unverified Twitter account @TheBillRussell, which had no avatar and since being created earlier this month had tweeted only once previously. The NBA on Tuesday confirmed the account was Russell's, per Bleacher Report.

"Proud to take a knee, and to stand tall against social injustice," the photo's caption reads, followed by multiple hashtags: #takeaknee, #medaloffreedom, #NFL, #BillRussell and #MSNBC.

Subsequent tweets at the account asked if Russell, in fact, tweeted the photo. The reply: "Yes I did." When other tweets — including from Twitter's verified sports feed — asked that the account be verified, the account replied, "We are trying."

Russell, 83, was a civil rights activist in the 1960s as well as one of the NBA's dominant players and a pioneer as the first African-American coach in one of America's major professional leagues.

He was awarded the Presidential Medal of Freedom, the nation's highest civilian honor, in 2011 by President Barack Obama.

Comments by current President Donald Trump about NFL players kneeling during the national anthem have ignited a firestorm of reactions from across sports.