Watch: "It's nice to see everyone", says RJ Mitte at Breaking Bad reunion

US actor RJ Mitte, best known for his role as the defiant son of drug kingpin Walter White in the drama series Breaking Bad, has died aged 34.

"It is with profound sadness that we share the tragic passing of beloved actor, philanthropist, and passionate disability rights advocate RJ Mitte," his representative told the BBC.

He died in Brownsville, Texas. No immediate cause of death was provided.

Mitte, who lived with cerebral palsy, drew on his own experience for his role as Walter 'Flynn' White Jr in the Emmy-winning drama series starring Bryan Cranston and Aaron Paul. He earned a Screen Actors Guild Award in 2014 for his work on the series.

RJ Mitte (right) as Walter White Jr. alongside Bryan Cranston (left) and Anna Gunn (centre) in series one of Breaking Bad in 2008

"Mitte brought authenticity to the role and built a platform on disability awareness and inclusion," his representative, Sean Reilly, said in a statement to the BBC.

Mitte also served as an ambassador for United Cerebral Palsy and Shriners Children's.

He created The Mitte Foundation as well, to support philanthropic efforts and community initiatives, using his platform "to challenge stereotypes and promote greater representation for people with disabilities", Reilly said.

The Brownsville Police Department confirmed the actor's death in a statement to the BBC, saying the cause and manner of death have not been determined and the investigation remains ongoing. No foul play was suspected, according to police.

The actor was declared dead on 12 October at what was believed to be his home, Cameron County Justice of the Peace, Cyndi Hinojosa, told the Associated Press, adding that a post-mortem examination would be performed.

Breaking Bad aired on US cable broadcaster AMC for five seasons from 2008-13.

Cranston posted a tribute to his on-screen son on Instagram, writing that he was in "deep despair" following news of Mitte's death.

The anti-hero drama created by Vince Gilligan earned a whopping 58 Primetime Emmy nominations and won 16, including two for Outstanding Drama Series in 2013 and 2014.

Cranston plays a high school chemistry teacher in New Mexico who turns to a life of crime to support his family after a cancer diagnosis. As he descends deeper into the underbelly of the meth trade, he drifts further from his son, Walt Jr, who makes his displeasure known with levity through much of the series.

"I met him when he was only 14 years old when he was cast as Walter White Jr., a part he played with such joy and enthusiasm," said Cranston.

"That kid was pretty raw when we started shooting the pilot in February of 2007, but little by little we watched him grow into a really fine actor."

Cranston wrote of Mitte's advocacy for performers with disabilities, and noted that he never allowed his cerebral palsy to "be an excuse for anything".

"All that promise and potential now is such a loss," wrote the actor, adding that he "thoroughly enjoyed being with him throughout the years on the series, and after the spotlight on Breaking Bad dimmed".

In a statement shared with the Hollywood Reporter, Aaron Paul, who played one of the show's lead characters, Jesse Pinkman, said he was at a loss and heartbroken.

"RJ, I love you my friend. You will be missed," he said. "And to whoever happens to be reading this, please know you are loved, and you are not alone. Always remember that."

Dean Norris, who played Mitte's uncle, Hank Schrader, posted that although "RJ didn't play my TV son, I always looked out for him as a young kid on set".

"He was a sweetheart of a young man and will be greatly missed," Norris wrote.

Mitte, who grew up in Louisiana, was a young teen when he auditioned for the breakthrough role after moving to Los Angeles to support his younger sister's acting career in 2005.

He had said that his first audition in Los Angeles was for a California state public service announcement for an anti-meth commercial.

"Fast forward to auditioning for Breaking Bad, which is still, in my opinion, an anti-meth thing because it doesn't end well for anyone," he said on the Joe Vulpis Podcast earlier this month.

His character was based on Gilligan's late friend who had a more severe case of cerebral palsy and used forearm crutches, which Mitte did not require.

Mitte was seen as playing the role with honesty and accessibility, cracking jokes as a teen whose health condition was rarely mentioned in the series.

After shooting to fame, Mitte fought for more varied roles and complex depictions of characters with disabilities, both visible and invisible.

"Whenever awards season rolls around, we always hope to see a diverse group of projects that reflect all of us, in body and mind," he told the BBC in 2021.

"Watching the awareness grow around disability representation has been great to see, but breakthroughs sometimes come in pieces and moments instead of larger change," he said.

Mitte's other on-screen credits include Hannah Montana, Switched at Birth, Westhampton and his latest project, Talking to Strangers, which came out earlier this year.