Phillip Seymour Hoffman’s longtime partner said she “sensed” Hoffman had begun using heroin before he died of an overdose in February 2014.

In an essay for Vogue, Mimi O’Donnell explained that she was worried about Hoffman but was confident that he would go back to rehab after filming the third installment of Hunger Games in Atlanta. Before that, she explained that Hoffman attempted to detox on his own but the physical pain that came with it was unbearable.

“Within a day or two of returning, he started using again. At home, he was behaving differently, and it was making the kids anxious. We both felt that some boundaries would be helpful, and tearfully decided that Phil should move into an apartment around the corner,” O’Donnell wrote.

She recalled being presented with a huge red flag when Hoffman began drinking after 20 years of sobriety. She said Hoffman would have an occasional drink but she confronted him after suspecting he was on drugs. It was then he admitted to getting his hands on some prescription opioids but ensured her that “it was just this one time and that it wouldn’t happen again,” she wrote.

O’Donnell said that Hoffman went back to rehab the fall prior to his death, but she realized by November that his addiction was too much for her to handle. After coming home from filming Hunger Games, she said he started using heroin again and died three days later.

“I told him, ‘I can’t monitor you all the time. I love you, I’m here for you, and I’ll always be here for you. But I can’t save you’.”

The details of Hoffman’s death were front-page news within hours: The 46-year-old was found with a needle in his arm surrounded by drugs in the bathroom of his Greenwich Village apartment, according to the New York Post.

O’Donnell wrote, “I had been expecting him to die since the day he started using again, but when it finally happened it hit me with brutal force. I wasn’t prepared. There was no sense of peace or relief, just ferocious pain and overwhelming loss.”

“The most difficult—the impossible—thing was thinking, How do I tell my kids that their dad just died? What are the words?”

Four years later, O’Donnell said that she and her three kids are only just now able to talk about Hoffman without bursting into tears.

“We talk about him constantly, only now we can talk about him without instantly crying. That’s the small difference, the little bit of progress that we’ve made. We can talk about him in a way that feels as though there’s a remembrance of what happened to him, but that also honors him,” she wrote.

“We open up, and it brings us together and keeps his spirit alive.”

[Featured Image: Mimi O’Donnell and Phillip Seymour Hoffman/AP Photo/Evan Agostini]