Hayden Panettiere appeared to be struggling in her personal life while filming her final movie, according to co-star Justin Chatwin.

Chatwin opened up about his experience making the thriller Sleepwalker, which was shot in 2025 and released in January.

The actor told People that Panettiere — who died at the age of 36 on Sunday — seemed to be “struggling” at the time.

The two first met when the actress was starring in her breakout NBC series, Heroes, then they reconnected on Sleepwalker, where Panettiere played a woman who loses her daughter in a car crash.

“Hayden seemed different when I met her this time than when I met her in the early years,” Chatwin said. “I’ve been sober for 15 years, so I know this world of addiction, and Hollywood — it takes, and it takes from youth. I could tell she was struggling, and I was like, ‘I don’t think it’s this movie.’ There’s a handful of women that I’ve worked with that I really liked, and I really loved working with her, but I also know that she was really lonely. … We hit it off great and it was an awesome shoot, but it was about domestic abuse, and it was subject matter that may have hit close to home, because she did mention it.”

While making Sleepwalker, Panettiere told Chatwin about the “struggles she’s had with trauma.” The actress and mother had been open about her issues with addiction and postpartum depression, and wrote about both in her candid memoir, This Is Me: A Reckoning, published in May.

“I’m sure that everyone else is going to say ‘Oh, she’s amazing, she’s such a sweet person on set,'” he added. “Because she was. But we’re trained to be actors, so we’re acting on set, you know? And she is sweet. She had a beautiful heart. But we’re trained to be on, and I really liked spending time with her because she took that off, and she was authentic with me about her life and she opened up about her struggles with addiction.”

In addition, the Nashville star’s former fiancé, Wladimir Klitschko, has spoken out. “Our family is going through a time of profound shock and grief,” the former boxing world champion posted on Instagram early Tuesday.

Klitschko added the news of Hayden’s death “saddens me deeply. She left this world far too soon. Hayden was, although no longer my partner, an important part of my life and the mother of our daughter, Kaya.”

The circumstances of Panettiere’s death are under investigation. The Greenville County Coroner’s Office said she was found unresponsive and that her cause and manner of death remain pending further investigation.