Hayden Panettiere appeared to be ‘struggling’ and ‘really lonely’ late last year on the set of the thriller Sleepwalker, her costar Justin Chatwin said Monday following news of her tragic passing.Chatwin, 43, told People about his experience working on the film with Panettiere, who died at 36 following an apparent overdose Sunday. According to a logline for Sleepwalker, Panettiere played the role of ‘a grieving mother … haunted by the tragic loss of her daughter in a car accident that left her abusive husband in a coma.’Chatwin said the dramatic topic matter might have played a part in Panettiere’s temperament during production of the movie, which had been released in January.’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,’ Chatwin said. ‘She opened up to me about a lot of things.’He added: ‘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.’ Hayden Panettiere appeared to be ‘struggling’ and ‘really lonely’ late last year on the set of the thriller Sleepwalker, her costar Justin Chatwin said Monday following news of her tragic passing. Pictured 2022 in LA The Daily Mail has reached out to representatives for Chatwin for further comment on the story.Chatwin said he could see differences in Panettiere during their time making the film, as he had previously worked with her on the show Heroes.’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.’Panettiere in 2018 granted her former fiancé Wladimir Klitschko full custody of their daughter Kaya Evdokia Klitschko, 11, as she dealt with issues such as postpartum depression and substance abuse.Chatwin said in the interview that Panettiere had told him about her ‘struggles that she’s had with trauma’ as well as her time in rehab while they were making the motion picture.He praised Panettiere as a ‘sweet’ person who ‘had a beautiful heart,’ noting that she remained kind toward others amid her personal upheaval.’I’m sure that everyone else is going to say, “Oh, she’s amazing. She’s such a sweet person on set,” because she was,’ he said. ‘But we’re trained to be actors, so we’re acting on set, you know?’He continued, ‘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. Chatwin, 43, said in the interview that Panettiere had told him about her ‘struggles that she’s had with trauma’ as well as her time in rehab while they were making the motion picture Chatwin praised Panettiere as a ‘sweet’ person who ‘had a beautiful heart,’ noting that she remained kind toward others amid her personal upheaval. Pictured 2023 in NYC According to a logline for Sleepwalker, Panettiere played the role of ‘a grieving mother … haunted by the tragic loss of her daughter in a car accident that left her abusive husband in a coma”And who knows where it comes from? Does it come from Hollywood? Does it come from home? And a lot of times, it’s both.’Chatwin said he felt sadness and anger in the wake of Panettiere’s death, adding, ‘I want to point a finger at something for this, and it keeps happening.’She was delightful and super open and we had a great time together and I’m just saddened that another one got taken down. It’s not the first, you know, and it’s yearly, dude, and it’s like no one’s really addressing it.’Sleepwalker director-writer Brandon Auman told the outlet in a statement that he had been ‘completely gutted’ following news of Panettiere’s death, calling her ‘a bright, open, numinous spirit.’Auman said he kept ‘thinking back to our time on set and how much she taught me,’ praising the actress for her openness and honesty ‘and how it related to her character.’He added, ‘I’m keeping those conversations private, but I was struck by how complex and deeply introspective she was. She lived a dozen lives in one short beautiful life. I’ll miss her forever.’