Patton Oswalt is reacting to a huge development in the infamous Golden State Killer case, which his late wife, Michelle McNamara, wrote about before her unexpected death.

McNamara died in her sleep in 2016 due to a combination of prescription drugs and an undiagnosed heart condition while she was still working on her book, I'll Be Gone in the Dark, which chronicled her “obsessive search” for the serial rapist-turned-murderer. On Wednesday, The Sacramento Bee reported that a suspect in the case was arrested after a more than 40-year search. The Golden State Killer terrorized Northern California from the mid-’70s to the mid-’80s, alleged to have carried out at least 12 homicides and 45 rapes.

Oswalt responded to the big news on Instagram, and said he would be watching the press conference being held at the District Attorney Crime Lab in Sacramento on Wednesday.

"This is insane, looks like they've caught the East Area Rapist, and if that's true, they caught the Golden State Killer," Oswalt said while on a flight from New York to Chicago. "Think you got him, Michelle ... full tilt freak-out in effect."

"If they’ve really caught the #GoldenStateKiller, I hope I get to visit him," Oswalt also tweeted. "Not to gloat or gawk -- to ask him the questions that @TrueCrimeDiary wanted answered in her “Letter To An Old Man” at the end of #IllBeGoneInTheDark."

Oswalt carried on his late wife’s work after her death, helping to finish the book, which debuted at the top spot of The New York Times’ nonfiction bestsellers list last month. On its release date, Oswalt took a copy of the book to McNamara's grave marker, writing, "You did it, baby. The book is excellent, the writing brilliant. You tried to bring kindness to chaos, which was your way."

"I hope you know, sweetie. I feel like you know," he also tweeted last month when McNamara's book debuted at the top spot. "And I hope you know it when your work leads to his capture. #IllBeGoneInTheDark debuts at #1 on the @nytimes bestseller list. I’m so proud of you."

Oswalt married actress Meredith Salenger last November. ET spoke with the comedian in January, when he opened up about how his 8-year-old daughter with McNamara, Alice, has been getting along with Salenger.

Watch below:

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