Michelle McNamara stalked the Golden State Killer until the day she died.

In Michelle McNamara’s book about the Golden State Killer, titled I’ll Be Gone in the Dark, she writes, “If you commit murder and then vanish, what you leave behind isn’t just pain but absence, a supreme blankness that triumphs over everything else.”

McNamara is referring to a man allegedly responsible for more than 50 rapes and 12 murders – a criminal who she became obsessed with unmasking.

“The unidentified murderer is always twisting a doorknob behind a door that never opens,” she continues.

“But his power evaporates the moment we know him. We learn his banal secrets. We watch as he’s led, shackled and sweaty, into a brightly lit courtroom as someone seated several feet higher peers down unsmiling, raps a gavel, and speaks, at long last, every syllable of his birth name.”

After a 42-year investigation that spanned continents, US authorities have this week announced they believe they may have solved one of the countries most disturbing cold cases.

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But McNamara, who tragically died in 2016, will never see the day that man, Joseph James DeAngelo Jr sits in a courtroom.

During the last years of McNamara’s life, the true crime writer would tuck her daughter into bed, say goodnight to her husband – the prominent stand-up comedian and actor Patton Oswald – and sit at her 15 inch computer hour after hour, investigating the case of the Golden State Killer, also known as the East Area Rapist.

She knew he was Caucasian and athletic, and roughly knew his age. She was familiar with his bizarre modus operandi; attacking women in the middle of the night, wearing a ski mask and naked from the waist down. If anyone else was home, the Golden State Killer would place dishes on their back, meaning if they moved, or attempted to call the police, he would hear.

In I’ll Be Gone in the Dark, McNamara writes, “Their fear found direction when they heard the voice, described as a gutteral whisper through clenched teeth, abrupt and threatening…”

And then, they just might have found him.

Authorities said they began a surveillance operation on DeAngelo Jr’s house and collected a “discarded DNA sample”. He was arrested this week.

Upon his arrest, Patton Oswald tweeted, “Goodnight, Michelle. You did good. You aimed a light and helped the hunters catch a monster…”

Goodnight, Michelle. You did good. You aimed a light and helped the hunters catch a monster. (Photo credit @vonswank) #MichelleMcNamara #IllBeGoneInTheDark #GoldenStateKiller pic.twitter.com/NYrc7dN16k

— Patton Oswalt (@pattonoswalt) April 26, 2018

Although authorities have been reluctant to connect the Golden State Killer’s arrest with the release of McNamara’s book, it is unequivocal her work generated increased interest in a case that had long gone cold.

Some were quick to point out that even news of finding the ‘Golden State Killer’ was a testament to McNamara, who coined the nickname during her research.

Oswald also tweeted: “If they’ve really caught the #GoldenStateKiller I hope I get to visit him. 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.”

McNamara stalked the Golden State Killer until the day she died. If only she knew what a day in April, 2018, would hold.