Hayden Panettiere died at 36, her family announced Sunday. No cause of death was given, and an investigation is ongoing. Authorities found no signs of trauma or foul play.

Panettiere had spent the months before her death promoting a memoir, "This Is Me: A Reckoning," released in May. The book detailed her rise through child stardom, her struggles with addiction and postpartum depression, and the domestic abuse she experienced as an adult.

She started her public life before she could walk. "I started baby modeling at 8 months old," Panettiere said in an interview with Yahoo tied to the memoir. "I did my first commercial at 11 months old. It was just so militant. No questions asked. I was a little soldier."

In the memoir, she wrote that the professional environment of her childhood rewarded her for suffering on screen. "Grown-ups gave me positive attention when — as an actor — I failed, got sick, screamed and cried, killed, grieved, and suffered," she wrote. "Reality merged with my imagination and burrowed into my core memories, where all my shame and trauma lives."

Panettiere wrote that a member of her public relations team gave her pills before interviews and red carpet appearances when she was a teenager. "I didn't ask questions, and she didn't formally seek my consent, but I didn't think twice," she wrote. "I trusted the people I worked with — especially my team — so I popped the pill in my mouth and swallowed." She described those pills as "the gateway drug that ushered me toward the good of pharmaceuticals and the downfall of addiction."

Her role as Juliette Barnes on "Nashville" became, by her own account, an unbearable parallel to her private life. The character dealt with postpartum depression, alcohol and pill dependency, and a failing marriage. "Every time I read the day's script, it was like I was looking in a funhouse mirror, seeing a distorted reflection of myself," Panettiere wrote. "I can't tell you how lost this made me feel."

She drew a direct line between the character and her own condition at the time. "I was suffering from debilitating anxiety and an addiction I couldn't shake, and I had to live through it twice," she wrote. "First at home, as Hayden, and then in front of millions, as Juliette."

At the height of her addiction, she wrote, alcohol was the first thing on her mind each morning. "Not my child, not my job, and not the rest of my life," she wrote. "I needed a drink to function." She entered rehab. The memoir described alcohol as something that let her say, in her words, "F*** it, I'll deal with everything later," delivering relief within 30 seconds.

The book's prologue contained the line that has circulated widely since her death. "One thing I know from my 36 years in the public eye is this: Life is a process that evolves day by day, year by year, and — like it or not — you are engaged in a cycle of growth until the moment you take your last breath." She also wrote, "I never want to stop evolving and changing for the better, and I'll forever be a work in progress."

In interviews around the memoir's release, she said she wrote the book to understand how early fame had distorted her sense of love, approval and self-worth — and that she hoped to leave the world a better place.

Panettiere was best known for playing Claire Bennet on the NBC series "Heroes" and Juliette Barnes across multiple seasons of "Nashville." She was 36 at the time of her death.