Breaking Bad star Bryan Cranston says he is in “deep despair” at the death of RJ Mitte, 34, who played his son on the popular TV show.

Mitte, who was best known for his role as Walter White jr in the hit series, took his own life on Monday (local time) in Texas.

Diagnosed with cerebral palsy aged three, he became a successful actor thanks to his role alongside Cranston and Aaron Paul.

He also advocated for other actors in Hollywood with disabilities.

In an emotional tribute, Cranston it was devastating that Mitte took his own life.

“We were texting each other just a few weeks ago — figuring out when we could meet for lunch. I don’t know if that lunch would have changed his future,” he wrote in Instagram.

“But I do know that I loved him, and thoroughly enjoyed being with him throughout the years on the series, and after the spotlight on Breaking Bad dimmed.”

Cranston said he met Mitte when he was only 14 years old and cast as his “sweet son” on Breaking Bad — “a part he played with such joy and enthusiasm”.

“Born with Cerebral Palsy, he never — ever — allowed that challenge to be an excuse for anything. He met the demanding shooting schedule head on with great determination.

“Always listening to the advice that his TV parents (Anna Gunn and myself) gave him — but being a teenager, sometimes mischievously ignoring the counsel in order to learn the hard way… He was one of the stars of a hit TV show — but still a kid.”

Cranston said he watched Mitte develop from a “raw” actor during the pilot in 2007 to “a really fine actor”.

“All that promise and potential now is such a loss.”

Mitte’s representative confirmed his death in a statement.

Mitte’s representative said in a statement: “It is with profound sadness we share the tragic passing of beloved actor, philanthropist, and passionate disability rights advocate RJ Mitte.

“Beyond entertaining friends and family around the world, he served as an ambassador for United Cerebral Palsy and Shriners Children’s.”

The actor was working on some upcoming projects that have come to a halt.

TMZ said he was due to star in the film Forgotten Outlaw, which was in pre-production when he died, and he was halfway through a limited series, Like It Was Yesterday, exploring near-death experiences.

News of Mitte’s death comes just a year after he announced his engagement to Kennedy Suarez, after proposing on her 30th birthday.

“I’m thrilled to have found my person, my partner in life who makes me want to be better, no matter what we’re doing,” he told People at the time.

“Kennedy is my everything and I can’t wait to officially start our life together and see what adventures life takes us on next.”

Following the proposal, Suarez took to Instagram to share her excitement, writing: “My 30th felt like a fairytale…. I have the man of my dreams by my side we are doing what we love most — helping others.”

Mitte is survived by his parents, and younger sister Lacianne.

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-with AAP