Mimi O'Donnell has recently opened up about her longtime partner Philip Seymour Hoffman's drug addiction. The Hunger Games star died of acute mixed drug intoxication on Feb. 2, 2014.

Mimi O'Donnell Remembers Philip Seymour Hoffman

In the article she wrote, O'Donnell recounted Hoffman's struggle with drugs and alcohol but said that the actor was already 10 years sober before he relapsed. A slew of negative things happened to Hoffman, which encouraged him to start drinking excessively again.

Months after his continuous drinking, Hoffman started taking drugs again. O'Donnell confronted her partner about it and he said that it was just a one-time thing.

However, after Hoffman completed his Broadway stint on Death of a Salesman, his drug use escalated quickly. He started taking heroin again and he told O'Donnell that they were all prescription drugs.

Unsure where Hoffman got his opioids, O'Donnell already predicted that something bad will happen to the actor if he didn't stop taking heroin.

"I told him, 'You're going to die. That's what happens with heroin.' Every day was filled with worry. Every night, when he went out, I wondered: 'Will I see him again?'" wrote O'Donnell.

After he returned home from Atlanta, Georgia for the filming of The Hunger Games, O'Donnell noticed that Hoffman's heroin addiction has worsened.

O'Donnell said that things happened so quickly. One day, she was asking her friends to keep an eye on Hoffman and three days later, the actor was dead.

Dead At 46

Hoffman was found dead in the bathroom of his New York apartment with a syringe in his left arm. Toxicology reports revealed that there were several drugs in his system including heroin, cocaine, amphetamine, and benzodiazepines.

Police officers also found nearly 50 envelopes labeled "Ace of Spades" in Hoffman's apartment. Officers believed that the envelopes contained heroin. There were also used syringes and prescription drugs in his New York home.

Dr. Sanjay Gupta, CNN's chief medical correspondent, explained the dangers of taking multiple drugs at the same time. Most addicts who are used to taking drugs no longer feel its effects.

"They're not feeling it, but it's still having an impact on their ability to breathe, and that's the real problem," said Gupta. "It's called stacking. You can stack the same drug close together, or you can start to stack other drugs, one on top of the other. That's how people get into trouble. They do call it accidental death as well."