Kevin Tapia and his daughter Quinn, watch as authorities search in connection with the arrest of a man on suspicion of murder, Wednesday, April 25, 2018, in Citrus Heights, Calif. The Sacramento County District Attorney's Office plans to make a major announcement in the case of a serial killer they say committed at least 12 homicides, 45 rapes and dozens of burglaries across California in the 1970's and 1980s.(AP Photo/Rich Pedroncelli)
Kevin Tapia and his daughter Quinn, watch as authorities search in connection with the arrest of a man on suspicion of murder, Wednesday, April 25, 2018, in Citrus Heights, Calif. The Sacramento County District Attorney's Office plans to make a major announcement in the case of a serial killer they say committed at least 12 homicides, 45 rapes and dozens of burglaries across California in the 1970's and 1980s.(AP Photo/Rich Pedroncelli) Credit: Rich Pedroncelli

SACRAMENTO, Calif. — A man once sworn to protect the public from crime lived a double life, terrorizing suburban neighborhoods at night and becoming one of California’s most feared serial killers and rapists in the 1970s and ‘80s before leaving a cold trail that baffled investigators for more than three decades.

Former police officer Joseph James DeAngelo, 72, was behind bars Wednesday facing four counts of murder and, potentially, dozens of other charges after DNA linked him to crimes attributed to the so-called Golden State Killer.

The culprit also known as the East Area Rapist, among other names, is suspected of at least 12 slayings and 50 rapes in 10 counties from Northern to Southern California. The armed and masked prowler sneaked in through windows at night and surprised sleeping victims who ranged in age from 13 to 41.

When encountering a couple, he was known to tie up the man and pile dishes on his back. He threatened to kill both victims if he heard plates crash to the floor while he raped the woman. He then ransacked the house, taking souvenirs, notably coins and jewelry before fleeing on foot or bicycle.

Despite an outpouring of thousands of tips over the years, DeAngelo’s name had not been on the radar of law enforcement before last week, Sacramento County District Attorney Anne Marie Schubert said.

“We knew we were looking for a needle in a haystack, but we also knew that needle was there,” she said. “It was right here in Sacramento.”

A break in the case and the arrest came together in “light speed” during the past six days, Schubert said, though authorities refused to reveal what led to DeAngelo.

Sacramento Sheriff Scott Jones said detectives with “dogged determination” were able to get a sample of DNA from something DeAngelo discarded, though he wouldn’t say what the item was. The genetic material was not a match, but there were enough similarities for investigators to return for more and they said they were able to get a conclusive match.

After watching DeAngelo for several days, deputies took him by surprise Tuesday.

“It looked like he might have been searching his mind to execute some plan,” but never had time to act, Jones speculated.

DeAngelo was arrested on suspicion of committing four killings in Sacramento and Ventura counties, officials said. Ventura County District Attorney Gregory Totten said prosecutors would seek the death penalty.

DeAngelo, who served in the Navy, was a police officer in Exeter, in the San Joaquin Valley, from 1973 to 1976, at a time a burglar known as the Visalia Ransacker was active, Jones said.

He transferred to the force in Auburn in the Sierra foothills near where he grew up outside Sacramento. About 50 crimes, including two killings, were attributed to the East Area Rapist during the three years DeAngelo worked in Auburn, but Jones said it wasn’t clear if any were committed while on duty.

The wave of horrifying crimes had brought an end to a more innocent era in the Sacramento suburbs when children rode bicycles to school, played outside until dark and people didn’t lock their doors, Schubert said.

“It all changed,” said Schubert, who was 12 at the time. “For anyone that lived here in this community, in Sacramento, the memories are very vivid. You can ask anyone who grew up here. Everyone has a story.”