Rubin "Hurricane" Carter, the former professional boxer who became an advocate for the wrongly convicted after spending 19 years in prison for a triple murder he didn't commit, died Sunday in Toronto. He was 76.

Carter's struggle for freedom and exoneration was made famous in a number of books, a Bob Dylan song and a Hollywood film. Although born in the U.S., Carter had a special connection to Canada, where he settled following his prison release, which came about with the help of a group of Canadians.

Carter's work continued until his death. In a recent letter in the New York Daily News printed in February, Carter said he was on his deathbed, but that his "final wish" was for Brooklyn's district attorney to grant a hearing to David McCallum, a man who has been imprisoned for 28 years for a murder Carter said he didn't commit.

Carter was cremated Sunday and no funeral or memorial service has been planned.

A troubled past

Carter grew up in Paterson, N.J., where he had a number of run-ins with the law in his youth. He later joined the U.S. Army and started boxing, travelling through Europe and accumulating a series of wins.

When he left the army, his troubles with the law continued and he ended up serving four years in prison, convicted of robberies and assault.

Rubin "Hurricane" Carter stands over welterweight champion Emile Griffith after a first round punch, in Pittsburgh, Pa., Dec. 20, 1963. (Associated Press)

But he again turned his attention to boxing and turned pro in 1961. He began compiling an impressive record as a middleweight, scoring 11 knockouts in his first 15 fights.

Carter's rapid-fire combinations and punching power earned him the nickname "Hurricane" and, by 1963, The Ring Magazine had rated him number 10 in world rankings. In 1964, Carter got a title shot against middleweight champion Joey Giardello. But he lost in a 15-round decision and, over the next few years, his fight record was mixed.

His career came to an abrupt end when, on June 17, 1966, Carter and his acquaintance John Artis, were arrested for the fatal shooting of two men and a woman at the Lafayette Grill in Paterson.

Wrongly convicted

Although both professed their innocence and passed a lie-detector test, they were later charged with the murders.

Police had said Carter's car was similar to one spotted at Lafayette Grill. Investigators also had witnesses, two convicted felons who claimed they saw Carter and Artis come out of the tavern with guns in their hands. An all-white jury convicted the two and Carter was sentenced to three life terms in prison.

To live in a world where truth matters and justice, however late, really happens, that world would be heaven enough for us all. - Rubin Carter, in a Feb. 2014 letter printed in The New York Daily News

While in prison, Carter penned his autobiography: The Sixteenth Round: From Number 1 Contender to #45472. His book and a series of New York Times investigative stories raising questions about the case attracted attention and support from celebrities like Muhammad Ali and Bob Dylan (who co-wrote the song Hurricane).

By 1976, the two witnesses had recanted their story, and the New Jersey Supreme Court overturned the convictions. But in a second trial, one of the witnesses reaffirmed his original testimony. The prosecution also claimed that the murders were racially motivated and in retaliation for the killing of a black tavern owner by a white man that same day.

Carter and Artis were again found guilty.

Undeterred, their legal teams continued to try to prove their clients' innocence.

Canadian connection

In 1980, Carter received a letter from Lazarus (Lesra) Martin, a young teen who had read his autobiography. Martin, an American who was living and being tutored in a Toronto commune, met and befriended Carter.

"This little 15-year-old kid read my SOS and came to help me, and with him came his Canadian family," Carter told the New York Daily News in 1999.

The Canadians moved to New Jersey and helped Carter's legal team. They discovered a number of improprieties with the case, including documentation that the prosecution had suppressed evidence.

Carter's story was popularized in the 1999 film 'The Hurricane,' which starred Denzel Washington (pictured above on the right) in the title role. (Reuters)

With this new evidence, Carter's legal team launched a number of appeals. Although initially unsuccessful, a federal judge in 1985 finally ruled that the convictions of Carter and Artis were based "upon an appeal to racism rather than reason and concealment rather than disclosure."

"The jury was permitted to draw inferences of guilt based solely upon the race," of the defendants, the judge wrote. Carter was freed (Artis had been paroled in 1981) and in 1988 all indictments were dismissed.

Carter began a new life in Toronto, moving in with the Canadians who helped secure his freedom. But the relationship between him and the group became strained and Carter moved out, finding the rules of communal living too restrictive.

He spoke out against the justice system and became a strong advocate for individuals imprisoned whom he believed to be innocent.

Crusader for justice

In 1993, he helped found the Association in Defence of the Wrongly Convicted and became its executive director. Carter also became a motivational speaker, travelling around the world, sharing the stage with world leaders.

"Rubin made it his life’s mission to help others who had been wrongly convicted after his own exoneration for crimes he did not commit, but for which he spent 19 years in prison," the association said in a release. "Rubin will be remembered by those at AIDWYC who were fortunate enough to have worked with him as a truly courageous man who fought tirelessly to free others who had suffered the same fate as he."

His life was given greater exposure with the release of the 1999 film The Hurricane, starring Denzel Washington and directed by Canadian filmmaker Norman Jewison. Yet the movie came under some criticism for taking liberties with the facts, bolstering the role of the Canadians while downplaying the efforts of Carter's legal team and white-washing his criminal and violent past.

Carter joined with prominent African American community leaders on several projects to help wrongfully convicted inmates seek legal counsel. (Damian Dovarganes/The Associated Press)

In 2004, Carter broke ties with the Association in Defence of the Wrongly Convicted — upset it did not object more strongly when prosecutor Susan MacLean was named to the Ontario Court of Justice. MacLean had been involved in the case against Guy Paul Morin who was convicted in 1992 of murdering a young Ontario girl but later exonerated through the use of DNA evidence.

Carter continued his public speaking and advocacy and, in 2011, released the book Eye of the Hurricane: My Path from Darkness to Freedom.

"If I find a heaven after this life, I'll be quite surprised," he wrote in his letter to the New York Daily News. "In my own years on this planet, though, I lived in hell for the first 49 years, and have been in heaven for the past 28 years.

"To live in a world where truth matters and justice, however late, really happens, that world would be heaven enough for us all."