CNN  — 

“Nanny McPhee” star and climate change activist Raphael Coleman has died at the age of 25.

The British actor’s mother, Liz Jensen, confirmed his death in a tweet posted on Friday, February 7.

“Rest in peace my beloved son Raphael Coleman, aka Iggy Fox,” she wrote. “He died doing what he loved, working for the noblest cause of all. His family could not be prouder. Let’s celebrate all he achieved in his short life and cherish his legacy.”

His stepfather, Carsten Jensen, said on Facebook that Coleman “collapsed without prior health problems” during a trip.

“Raph wasn’t my child, even though I was close to him. But I can feel it myself. I see it in his mother’s eyes, and I hear it in her voice, the irreversible loss of the most precious thing in life,” Jensen wrote in the post.

Coleman was born in London and appeared in several movies as a child, including “The Fourth Kind” and “It’s Alive.”

He was best known for playing Eric Brown, aged 11, in the 2005 British comedy movie “Nanny McPhee,” alongside Emma Thompson, Colin Firth and Angela Lansbury.

After starring in several movies as a child, Coleman earned a degree in zoology and became a climate activist.

His former castmate, Eliza Bennett, said she was “heartbroken” at the news.

“After we worked on Nanny McPhee, he dedicated his life to protecting wildlife and fighting climate change,” she wrote.

Coleman gained a zoology degree and began traveling the world, according to his website, “working with wildlife and exploring wildernesses” and trying to make money through photojournalism and filmmaking.

He became an active member of the climate activism group Extinction Rebellion, according to his stepfather. “Under the name Iggy Fox, he controlled the group’s use of social media, spoke at demonstrations, and was arrested again and again,” wrote Jensen.

His mother called him a “courageous spirit of #ExtinctionRebellion” who “loved life so much.”

Extinction Rebellion posted a tribute to Coleman on its website. “You were a true warrior, who tirelessly worked on behalf of others, on behalf of all life,” said the statement. “You had the fire of youth and a wisdom that belied your age. The world has lost one of its fiercest and most dedicated defenders.”

Another activist organization, Occupy London, tweeted that it was a “tragic loss” of a “dedicated protector of animals” and “deep inspiration to all who met him.”

His mother thanked everyone for the “beautiful tributes to our beloved Raphael” on Twitter.

She said Extinction Rebellion would be “celebrating his remarkable life as a wildlife biologist and activist” on Thursday evening at London’s Brazilian embassy.

Coleman was arrested outside the embassy in August during a protest over deforestation in the Amazon.