Close your windows and lock your doors, friends, because the most prolific killer/rapist in California history is still at large. Between 1976 and 1986, this unknown subject raped at least 51 people and murdered at least 12 across the state of California—that we know of. He was originally known as the East Area Rapist for his tendency to select victims who lived in the eastern side of Sacramento, CA, but he later went on to victimize more people throughout the state, changing his MO as he moved further south. Michelle McNamara, true crime writer and author of the recently published account of this same criminal, I’ll Be Gone in the Dark, dubbed him the Golden State Killer after a series of brutal slayings by the Original Night Stalker were linked to the East Area Rapist via DNA.

And now, HLN has a brand new docuseries that not only brings us all up to speed on what the Golden State Killer has done but also highlights the progress that has been made in law enforcement’s efforts to catch him. The first episode of this five-part series premieres this Sunday, March 18th, at 9 p.m. ET/PT, and it will go over the motives, methods, and mind games of what is probably the scariest killer I’ve ever encountered in the countless true crime stories I’ve read about.

The episode begins with the firsthand account of victim Jane. Her calm and strength in the retelling of her rape—which occurred in the early '70s—is a testament to her character and her obvious drive to want to do whatever is in her power to help catch this man. The episode also details the rest of the East Area Rapist’s attacks in the Sacramento area, with firsthand accounts from the detectives who worked the cases then as well as the younger detectives who are still working to catch the perpetrator.

The docuseries does an excellent job of weaving in original news footage from the '70s and '80s along with those interviews to show context and just how pervasive the fear was in the area. The most chilling moments of all are when the show plays actual tape recordings of the killer’s voice—a voice directly out of our worst nightmares, one that shows the utter lack of remorse and perhaps even sick glee at his ability to cause so much fear and chaos.

The East Area Rapist’s first rape crime occurred in June 1976, and he just doesn’t stop. His crimes were brutal and bold as he broke into the homes of sleeping victims in the middle of the night and startled them awake with a flashlight in the eyes and sometimes a butcher knife or gun to the throat. When the news proclaimed that women who have men at home are safe from the rapist, he upped the ante and began raping women while their husbands or boyfriends were tied up. And it continued to get worse from there.

The evidence shows he’s vicious, smart, and exceptionally well prepared. Catching him seemed impossible after over 50 rapes by the middle of 1979, when suddenly, the attacks stop.

If you do a quick Google search on serious crime in California, it appears that the state is overrun with serial killers, rapists, and other types of criminals between the 1970s and 1980s. Technology then was not what it is today. DNA analysis didn’t exist, and neither did a statewide database where evidence could be cross-referenced with other crimes occurring in other precincts. In fact, citizens and police of one town in California (and this is likely true with the rest of the country) weren’t even aware of the brutal crimes of the East Area Rapist and other criminals because of the hyperlocal coverage by the media. The internet was pretty far from invention, and people tended to stay close to home.

Unmasking a Killer shows the extraordinary lengths the Sacramento police, and a couple of their very intrepid detectives, went through to connect the East Area Rapist to other crimes across the state by looking at motive alone and then confirming hunches via DNA matches in the 1990s. Law enforcement refuses to give up as the manhunt continues. The case is monumental in scope, and the new HLN original series—coupled with a $50,000 reward for information that leads to the capture and arrest of the EAR/ONS/GSK—is part of the FBI’s renewed purpose in catching him, an effort to finally bring peace to the victims and their families.

And once you’ve watched the show, which I highly recommend, and you’ve felt that it’s not enough, you can catch the podcast version of the show, also called Unmasking a Killer, where the producers discuss details of the show and release more information that didn’t make it into the docuseries. You can listen to the podcast on Mondays after each episode airs. If you’re a fan of true crime or have recently read Michelle McNamara’s groundbreaking book on the subject and are looking for that visual/aural element to get the most detail possible on the case as the East Area Rapist morphs into the Golden State Killer, catch Unmasking a Killer this Sunday on HLN.

Watch the trailer for Unmasking a Killer!

Ardi Alspach was born in Florida, raised in South Carolina, and now resides in New York City with her cat and an apartment full of books. By day, she's a publicist, and by night, she's a freelance writer. You can follow her on Twitter at @ardyceelaine or check out her website at ardyceelaine.wordpress.com.