(CNN)On the court, Boston Celtics legend Bob Cousy was known for his "unshatterable poise." When he led his team's famed fast-break, he handled the ball with such ease that one observer said it "seemed to have wings and a homing device."
What white players owe their black teammates: Boston Celtics legend's tears offer an answer
But there was one basketball moment where Cousy lost all sense of control. He couldn't talk. He choked back sobs. He covered his face with his outsized hands to mask his shame.
It came while he tried to explain his relationship with his legendary teammate, Bill Russell.
An ESPN crew was interviewing Cousy on camera about Russell when the conversation shifted to the racism Russell endured during the Celtics' heyday in the late 1950s and early '60s.
"We could've done more to ease his pain and make him feel more comfortable," Cousy told the interviewer. "I should've been much more sensitive to Russell's anguish in those days. We'd talk ..."
And that's when Cousy loses it. His face contorts in anguish, and he breaks down. The interviewer quickly moved on after Cousy regained his composure. But Gary M. Pomerantz, an author and historian, saw a replay of the 2001 film and wanted to know more. He gave Cousy a call.
The result of that conversation is "The Last Pass," a new book that examines the complex relationship between these two iconic athletes.
"It's rare in America for a 90-year-old white man to reconsider race and how it played out in his own life, but that's what Cousy is doing," Pomerantz said. "He's not gilding any lilies. He's pointing out his flaws and admitting to them."
Cousy, or "Cooz" as he is commonly known, said he never anticipated the torrent of guilt he experienced when ESPN asked him about the man he calls "Russ." But he wondered if he should have done more for Russell; after all, Cousy had been the captain of the Celtics and the symbol of the team in Boston.
"I had this in my subconscious, of not having done enough for Russ," he told CNN. "It had been repressed. Something had brought it out."
"The Last Pass" isn't just about the past. It raises a question about the present: What do white athletes owe black teammates they've befriended when those friends take a public stand against racism?
Cousy isn't the only white athlete to ask if he should have done more. And plenty of white athletes face that question today, as more black athletes use their public platforms to protest racial injustice.
Cousy says telling other white players what they should do is not his style. He said white athletes should follow their own conscience when a black teammate speaks out.
One of history's most iconic sports photographs captures the choice one white athlete made. It shows two African-American sprinters giving a black power salute from the victory stand at the 1968 Olympic games as the national anthem was played. The two men