“In one of the saddest moments of our lives, we are not able to find the appropriate words to express the pain in our hearts," the statement continued. "As we grieve, we ask that you respect our privacy. And, while we mourn the loss of this sweet and gracious man, we also wish for all to celebrate his indomitable spirit and love of life."
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He is the younger brother of actress Jane Fonda and the son of Henry Fonda.
Fonda co-wrote and co-starred in "Easy Rider" with his friend Dennis Hopper.
In one of his last interviews, he told The Hollywood Reporter in March that the budget was so tight for the film that he and its makers decided to use New Orleans' Mardi Gras as a locale to save money on actors.
"We'd have 100,000 people or more in costumes on the streets, and we wouldn't have to pay them," he told the publication.
Fonda made his acting debut in the 1961 Broadway production "Blood, Sweat and Stanley Poole" but soon found his niche as a star of the emerging counterculture in the films of director Roger Corman.
After 1969's "Easy Rider" he appeared in a long string of films, including "Escape From L.A." in 1996 and "Ulee's Gold" in 1997, the latter of which earned him an Academy Award nomination.
He also appeared in "The Passion of Ayn Rand," a 1999 made-for-TV movie, and the box-office success "Ocean's Twelve" in 2004.
Like his sister, Fonda could be outspoken. In June 2018, he took heat for a tweet criticizing the Trump administration for separating migrant children at the U.S.-Mexico border and subjecting them to unsanitary, prison-like facilities.
He suggested on Twitter that young Barron Trump, the president's son, should be put "in a cage" with pedophiles. He soon apologized.
"Like many Americans," he said in a statement to Fox News, "I am very impassioned and distraught over the situation with children separated from their families at the border, but I went way too far."
On Friday, the Hollywood Chamber of Commerce, which administers the Walk of Fame, announced that flowers would be placed at Fonda's star next to to the Hollywood Roosevelt Hotel. It was dedicated in 2003.
Janelle Griffith is a breaking news reporter for NBC News.
Diana Dasrath is an entertainment producer and senior reporter for NBC News covering all platforms.