Lauren Clark is a "48 Hours" producer. She writes about investigation into the search for a man who terrorized California for a decade. Learn more about the case in "48 Hours" "The Golden State Killer."

While working on this story about the efforts to catch the Golden State Killer – even in the "48 Hours" offices, full of true-crime journalists – the first reaction was often "How did I not know about this?" Though the case has been under the public radar for over 40 years, the identity of this prolific criminal has been a mystery, confounding generations of investigators across California. A big reason for this lack of awareness of his 10-year spree – 50 rapes and 12 murders from 1976 to 1986 – is how careful the Golden State Killer was to cover his tracks and not be caught. But, it also took a long time for authorities to definitively tie all of the crimes to the same perpetrator. Until recently, most people simply did not know that one criminal committed all of these offenses.

Through his fairly distinctive M.O. of breaking into his victims' homes in the middle of the night, tying them up in similar ways, and vanishing into the night, Sacramento investigators in late 1976 quickly identified that they had a serial rapist on their hands. He was then dubbed the East Area Rapist – EAR for short – due to the majority of crimes on the eastern area of the city and its suburbs. For months, the rapist terrorized the same few communities – sometimes striking multiple times a week. But as local media, authorities, and citizen patrol groups became more vigilant, he began to spread to different areas – committing assaults in nearby Stockton, Modesto, San Jose and Contra Costa County.

Multiple investigators told "48 Hours" that as his attacks spread south, it would usually take a little while for jurisdictions to connect the M.O. back to the East Area Rapist, but soon, precincts began to warn each other that he was on the move. After a little more than three years and about 50 rapes and sexual assault attempts, the offender seemed to suddenly disappear from Northern California.

We now know that he moved south and escalated his tactics, but when the murders began in Southern California in late-1979, they were not immediately connected to each other. In all, 10 people were killed between 1979 and 1986, spread out between Santa Barbara, Ventura, and Orange counties.

Though some suspected a link between the homicides, it wasn't until 1996 that advancements in DNA technology allowed for a connection to be made between the Janelle Cruz 1986 murder in Irvine and Manuela Witthuhn's homicide there five years earlier. Soon connections to the deaths of Dr. Robert Offerman and Debra Manning in Goleta, Lyman and Charlene Smith in Ventura, and Keith and Patrice Harrington in Dana Point followed. The name given to the unknown perpetrator in this series was: "The Original Night Stalker."

Some of the investigators in Northern California thought that the EAR was capable of murder, and thought that he could have moved on to become the Original Night Stalker, but it was not an easy connection to make. DNA science was not used in the 1970s, and tests were not easily run until the 1990s. Though rape kits were taken from the early crimes, their full value was not known, and many samples were lost or thrown out over the years. Luckily, some samples did remain from the Contra Costa crimes. In 1997, DNA testing confirmed that those rapes were indeed committed by the same attacker. Still, it took a few more years for authorities from Northern and Southern California to connect, but in 2001, forensic testing confirmed that the East Area Rapist and the Original Night Stalker were the same person. The new moniker? EARONS. Not quite "Jack the Ripper." When true-crime writer Michelle McNamara began looking into EARONS, she saw that the case needed a rebranding to be more easily identifiable and illustrate the extent of his crimes. In a 2013 article for Los Angeles Magazine, she gave him the name "The Golden State Killer."

HAVE INFORMATION?

The FBI released sketches made by three witnesses in an renewed attempt to catch a California serial killer. FBI

The FBI urges anyone with information on the Golden State Killer to call their tip line at 1-800-CALL-FBI or go to tips.fbi.gov.