Patton Oswalt is telling the horrifying story of the day he found his late wife, Michelle McNamara, not breathing in their bed.

McNamara, a crime writer, died in her sleep at the couple's home in Los Angeles in April. She was 46 years old.

In an interview with The New York Times, Oswalt says McNamara was obsessively working on her book, The Golden State Killer, at the time, and because he was worried about her health, he suggested a night to "sleep until you wake up." Oswalt says McNamara took some Xanax and went to bed.

WATCH: Patton Oswalt Talks How He and His Daughter Are Coping With His Wife's Devastating Death

After driving their 7-year-old daughter, Alice, to school and picking up some coffee for her, Oswalt says she was still snoring at 9:40 a.m. when he returned. However, after he took care of some business in his home office, he returned to his bedroom at 12:42 p.m. and realized she wasn't breathing. The paramedics arrived, and they pronounced her dead.

Although the coroner's office has still not declared a cause of death, Oswalt says he believes his wife overdosed on Xanax.

"I have a feeling it might have been an overdose," he says. "That's what the paramedics there were saying while I was screaming and throwing up."

"I was literally blinking trying to get out of this," he recalls about the nightmarish scene.

Still, he doesn't count the moment as the worst day of his life.

"The worst is when I told my daughter the next day," the 47-year-old Veep actor explains.

Oswalt went to counseling to deal with his grief, and candidly admits to at one point, turning to alcohol.

"I found out the hard way these past few months that alcohol really doesn't help," he says.

Returning to performing stand-up has actually helped him deal with the tragedy.

"[Getting on stage is] a rebuke to grief, an acceptance of the messiness of life," he notes. "I'll never be at 100 percent again, but that won't stop me from living this."

These days, the comedian says he and his daughter keep McNamara's memory alive by sitting down together and writing three things they remember about her every night.

"It keeps this living portrait of her," he says, getting emotional.

WATCH: Patton Oswalt Shares Powerful Post About Grief, Vows to Finish Late Wife's Unfinished Book

Last month, Oswalt dedicated his Emmy award for Outstanding Writing for a Variety Special to McNamara.

"Every bit of growth that I've had in my career, especially in my writing and my performing, came because I met Michelle McNamara," Oswalt told reporters backstage. "Because I met and married this woman who just was so much wiser and self-actualized and aware of life than I was. I had convinced myself that I was aware and self-actualized and mature, but then I met the real deal."

"To have that ripped out of my life the way that it has this year -- I’m not trying to say that this is meaningless, but everything seems like the lights have been turned down 50 percent on everything since she's gone," he continued. "It's just going to be a long, long time before I can be the kind of person she made me again."

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