Matt Damon has joined the escalating outrage over Gov. Rick Snyder’s handling of the water crisis in Flint, Michigan and has called on embattled governor to step down from his post.

“At the very least he should resign! At the very least,” the Hollywood actor and co-founder of the nonprofit Water.org told The Daily Beast at the Sundance Film Festival on Saturday.

“Listen, everybody’s entitled to a fair trial in the United States of America, but that man should get one. And soon. That’s just my personal opinion.”

Flint’s water disaster started back in April 2014, when an unelected state official switched the city’s main water supply from Lake Huron to the Flint River to save money. This ill-fated move has corroded Flint’s aging pipelines and exposed the city’s 102,000 residents—especially children—to the potentially crippling effects of lead poisoning and led to two outbreaks of Legionnaires Disease that has killed 10 people.

To make matters worse, emails released last week revealed that Gov. Snyder and his administration knew about Flint’s water quality issues as early as February 2015 but his administration said the problems would eventually “fade in the rearview.”

Gov. Snyder did not acknowledge the unsafe condition of the city’s water until Sept. 30, 2015. The governor apologized to the city in December. President Barack Obama has since declared a state of emergency and is allocating $80 million in new funding to Michigan to bolster its cities’ water infrastructures.

The Martian star co-founded his water advocacy nonprofit with Gary White to advocate for safe and clean water to citizens worldwide.

“In terms of the work that we do, to see it happening in Flint, every parent in America feels it on a visceral, deep level, because we ask the question, ‘What if that was my child?’” Damon, a father of four daughters, told The Daily Beast.

“It’s unconscionable in Flint, and it’s unconscionable that 663 million people around the world are dealing with that every day in the developing world,” he continued. “Those are the communities we interact with, and that’s the mission of Water.org: to end that suffering for those children, and those parents.”