By Karina Tsui, Alex Stambaugh, Holly Yan, CNN

(CNN) — Actress Hayden Panettiere, known for portraying an indestructible cheerleader in the series “Heroes” and a country music sensation in the show “Nashville,” is dead after she was found in cardiac arrest Sunday at a residence in South Carolina, a coroner’s office said. She was 36.

No official cause of death has been released.

Panettiere soared to stardom in the early 2000s before stepping back from the public spotlight as she battled challenges with addiction and mental health. She recently released a memoir describing her struggles and spoke publicly about the pain of losing her brother.

Emergency personnel responded to a 911 call about a “reported cardiac arrest” in Greenville on Sunday afternoon, the Greenville County Coroner’s Office said in a release Monday.

The California resident was found unresponsive inside the South Carolina home “where she had been temporarily staying,” the coroner’s office said. The address is at an apartment complex, local police said.

Medical personnel found Panettiere in cardiac arrest and tried to resuscitate her, but the efforts were unsuccessful, the coroner’s office said. Panettiere was pronounced dead about a half hour after the 911 call.

An autopsy performed Monday revealed no signs of trauma that would have contributed to her death, the coroner’s office said. But the official cause and manner of death are still pending the results of additional testing.

The 911 call came from an acquaintance, Greenville police said without elaborating about the person.

“It is with profound sadness that we share the tragic passing of our beloved Hayden. She was an incredible light and a force of nature who brought immeasurable love and joy to all who knew her — and to the millions who watched her onscreen,” her father, Skip Panettiere, said in a statement shared by her representative.

The actors’ union SAG-AFTRA mourned the “sudden passing of Hayden Panettiere,” who had been a member since 1994, the union said in a statement. “A child actor, Hayden’s long career in TV & film included memorable roles in ‘Heroes,’ ‘Nashville’ & more. Our hearts are with her daughter, family, friends & fans.”

Panettiere was born August 21, 1989, in Palisades, New York. Her career started when she was 11 months old, appearing in commercials.

She became one of the youngest people ever nominated for a Grammy Award for voicing Princess Dot in the 1998 movie “A Bug’s Life.”

She played Lizzie Spaulding on the CBS soap opera “Guiding Light” from 1996 to 2000, portraying a girl with leukemia.

Even as a child, Panettiere displayed a remarkable work ethic, her “Guiding Light” co-star Bethany Joy Lenz posted on Instagram.

By the time Panettiere was 10, “she knew her lines and everyone else’s,” Lenz wrote. “Her intelligence was astonishing. She understood scenes and nuance and human struggle like no child I’d ever seen on camera.”

Fans also remember Panettiere for her role in the 2005 film “Ice Princess” alongside Michelle Trachtenberg, who died in February 2025 due to complications of diabetes mellitus.

Panettiere’s breakout role came when she was a teenager, playing the self-healing cheerleader Claire Bennet in the NBC television series “Heroes.” The show ran from 2006 to 2010.

In 2011, Panettiere appeared in “Scream 4” as Kirby Reed and returned to the horror franchise years later in the sixth installment. She also had notable roles in the films “Remember the Titans”; “Bring It On: All or Nothing,” a sequel in the anthology series of competitive cheerleading; and “I Love You Beth Cooper.”

Panettiere earned another starring role in ABC’s musical drama series “Nashville,” playing young country music star Juliette Barnes opposite Connie Britton from 2012 to 2018.

After widespread acclaim during her teens and 20s, Panettiere spoke openly about her struggles with addiction. She released a candid memoir earlier this year titled “This Is Me: A Reckoning,” reflecting on her life growing up from a child star to confronting postpartum depression, addiction, recovery and domestic abuse.

“I could relate to a lot of those storylines like the alcoholism and postpartum depression. They hit close to home,” she told People magazine in 2022.

At one point, she was hospitalized with jaundice, and doctors told her that her liver was “going to give out,” she told the magazine.

Panettiere shares an 11-year-old daughter, Kaya, with her former partner, Wladimir Klitschko, a Ukrainian former professional boxer.

In 2022, she opened up in an episode of “Red Table Talk” about the “very upsetting” experience of relinquishing custody of her daughter to Klitschko. Panettiere had previously said she was struggling with substance misuse at the time of that decision in 2018 and the issue wasn’t up for “discussion.”

“It was the hardest thing I could do,” she recalled. “But the best thing for my daughter was to make sure she was OK, take care of myself and make sure I could be a good mom to her. And sometimes that means letting go.”

Panettiere had also spoken about the loss of her brother, voice-over actor Jansen Panettiere, who died in 2023 at age 28 from an enlarged heart with aortic valve complications.

“There was nothing in my life that feels like losing my other half,” she told podcasterJay Shetty in an interview this year. “We were so close, and being the older sibling – who it’s your job to protect them and keep them safe – and not being able to, heartbreaking doesn’t even begin to cover it.”

Beyond acting and singing, Panettiere had also been known for her advocacy, supporting mental health awareness, animal rights and environmental issues.

She was honored by officials in Washington, DC, for her advocacy for DC voting rights and statehood, with the mayor proclaiming a “Hayden Panettiere Day” on September 16, 2011.

The actress publicly supported Ukraine after Russia’s invasion, launching a relief fund in 2022 to raise money for medical supplies and protective gear for Ukrainians.

Panettiere could not “continue to sit on the sidelines” and watch people suffer in the country where she has friends and family, she told CNN in 2022. Klitschko’s brother, Vitali Klitschko, is the mayor of Kyiv.

In recent years, Panettiere returned to acting with films such as “Amber Alert” in 2024 and “Sleepwalker” in 2026. The resurgence of her career made her death even more shocking.

“I don’t understand how this is real. Everything seemed to be turning around,” Lenz wrote. “She was coming BACK to life, wasn’t she? It’s too young and there’s still so much more life. And her daughter…. Hayden, you are surround by love. I’m sorry for every moment I didn’t reach out or check in. This can’t be real.”

This story has been updated with additional information.

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