Raphael Coleman, who starred alongside Emma Thompson and Colin Firth in the 2005 film Nanny McPhee, has died after collapsing on a run.
The British actor appeared in three feature films, It's Alive and The Fourth Kind in 2009.
He then studied zoology at the University of Manchester before dedicating himself to activism, working with the environmental movement Extinction Rebellion to advocate for wildlife conservation.
His mother Liz Jensen confirmed the news over social media.
"Rest in peace my beloved son Raphael Coleman," she said.
"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."
Coleman was also remembered by his stepfather Carsten Jensen.
In his statement on Facebook, Jensen recalled the individual stages of Coleman's growth into an adult, describing his stepson as an "old-wise, extremely literate" child who "loved to lecture adults with his always astonishing knowledge".
Jensen went on to discuss Coleman's global travels and his leadership within Extinction Rebellion, controlling social media, speaking at demonstrations and enduring numerous arrests in the name of the group's ideals.
"When I think of Raph, I see something that will never die, a blunt of eternity, a light beam that lives forever in young people," he said.
© RAW 2020