True-crime writer Michelle McNamara died of an accidental overdose on April 21st, 2016 — two years before the source of her obsession, the Golden State Killer, was arrested. Her drive to discover the identity of the prolific serial killer/rapist is captured in the upcoming six-part HBO documentary, I’ll Be Gone in the Dark, out June 28th. The doc shares a name with McNamara’s book, published posthumously in February 2018.

“I just obsessed over it,” McNamara says in a new teaser. “What drives me is the need to put a face on an unknown killer.” The film was directed by Emmy-winning, Academy Award-nominated Liz Garbus and produced by Story Syndicate. Additional directors include Elizabeth Wolff, Myles Kane and Josh Koury.

Over the course of the Seventies and Eighties in California, a mysterious man terrorized residents with a series of rapes and murders; he was suspected of committing at least 12 murders, 50 rapes, and 100 burglaries in California between 1974 and 1986. McNamara coined the name “Golden State Killer” in both her book and various articles and blog posts about the alleged serial killer, but he was also known as the East Area Rapist, the Original Night Stalker, and the Visalia Ransacker.

McNarama played amateur sleuth for years — haunted by a murder in her own childhood — delving into the history of the killer and those who tracked him, such as retired detective Paul Holes, who also appears in the doc. “She had material that other investigators had never seen,” he says in the teaser.

After her death, McNamara’s husband Patton Oswalt called on fellow investigator-journalists — and McNamara’s friends — Paul Haynes and Billy Jensen to help finish her book. The New York Times bestseller came out just months before Joseph James DeAngelo, a retired cop from California, was arrested in connection to the 1980 double homicide of suspected GSK victims Lyman and Charlene Smith. According to the New York Times, he was charged with 13 counts of murder and multiple kidnapping and weapons charges.

In March, DeAngelo offered to plead guilty in exchange for a life sentence. The Sacramento County District Attorney’s Office countered that they would continue to seek the death penalty.

Holes and Jensen launched a new podcast in the spring of 2019 called The Murder Squad, on which they attempt to solve cold cases with audience help.