Actress Hayden Panettiere, known for her roles in "Heroes" and "Nashville," died on Sunday at the age of 36. Her ex-fiancé, heavyweight boxing champion Wladimir Klitschko, confirmed her death on Tuesday, stating she "left this world far too soon."

Panettiere and Klitschko were engaged and are parents to their daughter, Kaya, born in 2014. Klitschko shared his deep sadness over the news on social media, describing Panettiere as an "important part of my life."

The Greenville County Coroner's Office announced that Panettiere was found in cardiac arrest prior to her death. An autopsy revealed no signs of trauma that would have contributed to her passing. The official cause and manner of death are still pending further investigation and additional studies.

Klitschko expressed his commitment to ensuring their daughter remembers her mother. "To our daughter Kaya, I will always speak of her mother with respect and make sure she remembers the person she was," he stated. He also extended condolences to Panettiere's parents, friends, and fans.

Panettiere, who began her career as a child star, had been open about her struggles with postpartum depression, addiction, recovery, trauma, domestic abuse, and loss. She detailed these experiences in her memoir, "This Is Me: A Reckoning," released in May. Klitschko acknowledged her talent and resilience, noting she built an "incredible career" while navigating the challenges of a demanding industry.

Her notable roles included Claire Bennet in the NBC series "Heroes" and Juliette Barnes in the ABC/CMT musical drama "Nashville." Her passing has prompted an outpouring of grief from fans and colleagues who remember her as an "amazing talent."

Klitschko shared a photo of himself with Panettiere on social media and requested privacy during this difficult time. He emphasized that "young and talented people like Hayden should not leave this world so soon."

Panettiere's career spanned television and film, establishing her as a prominent figure in Hollywood from a young age. Her public candor about her personal battles in her memoir offered a glimpse into the complexities she faced throughout her life and career.