SACRAMENTO — Just months after the breakthrough in the Golden State Killer cold case, police have used DNA and genealogical technology to nab another suspected serial rapist, believed to have terrorized women in six counties starting in the 1990s.

Authorities say UC Berkeley employee Roy Charles Waller, 58, of Benicia, the so-called NorCal Rapist, is responsible for at least 10 and possibly more attacks on women from Martinez to Sacramento, including one in which he posed as a trick-or-treater on Halloween night in 1996.

Waller was arrested without incident Thursday near his work place in Berkeley, identified by the same genealogy database that put suspected Golden State Killer Joseph DeAngelo behind bars earlier this year.

In 2006, investigators in the NorCal Rapist case were able to link 10 attacks to the same individual through matching DNA. After learning how DeAngelo was caught, the investigators created a special profile that could be submitted to GEDmatch. Investigators uploaded to information to the website 10 days ago, and the case was cracked days later, Sacramento County District Attorney Anne Marie Schubert said at a news conference Friday. GEDmatch allows users to voluntarily upload their DNA profiles onto the massive database, allowing users to find a lost relative — or, lately, helping police officers to track down long-sought killers and rapists.

“Genealogy 10 days ago led us very quickly to this individual,” Schubert said. “It was probably record-setting how quickly Mr. Waller was identified as the person we were looking for.”

According to court records obtained by the Sacramento Bee, once Waller was identified through the genealogy website, investigators collected two samples of his DNA from his trash can outside his house and linked the DNA from a straw to two 2006 attacks. Those records also indicate that the GEDmatch led to a “close relative of the NorCal Rapist” and that law enforcement narrowed him down using his physical appearance, previous addresses and his ownership of similar guns used in the crimes.

Investigators said it’s possible there are other victims out there, but Schubert said Waller is not suspected of committing any attacks on the Berkeley campus.

Waller has worked at UC Berkeley since 1992. He is a safety specialist in the Office of Environmental Health and Safety, training employees how to safely operate forklifts, aerial lifts and respirators, said university spokesman Dan Mogulof. The office is located at University Hall, a building that houses the School of Public Health just across Oxford Street from the university’s main entrance. The office was closed Friday afternoon with a handwritten sign on the door referring those with questions about Waller to campus spokespeople.

“We were shocked today to learn that a campus employee was arrested in connection with a series of rapes,” Mogulof said in a statement. Campus police “will be reviewing any open sexual assault cases to determine if any might be related,” he said.

The NorCal Rapist’s string of sexual assaults occurred between 1991 and 2006 and included the Halloween night attack in Martinez in 1996 and an assault in February 1992 in Vallejo.

Waller has been charged with 12 counts of forcible sexual assault related to attacks on two women in Sacramento on Oct. 14, 2006. Those charges carry special enhancements of using a gun that would carry a lifetime prison sentence and have no statute of limitations. He is being held in a Sacramento County jail without bail and is scheduled to be arraigned Monday at 1:30 p.m.

Former Contra Costa crime lab chief Paul Holes, who helped crack the Golden State Killer case, said he spent decades working on the NorCal Rapist case, too.

He recalled the horrific details of the Martinez assault. The victim was resting on her couch Halloween night when she heard the doorbell and she answered, thinking it was a late-arriving trick-or-treater.

The suspect, wearing a skeleton mask, tackled her, handcuffed her and carried her upstairs where he repeatedly raped her for hours. Holes said the suspect was “very evidence conscious,” cleaning and destroying various items. Police believe he phoned the victim at her dental office about two weeks after the attack and apologized.

Holes initially tied the Martinez rape to the Vallejo assault through DNA evidence. And when police obtained blood DNA from a 1997 rape in Chico where the victim stabbed the attacker with scissors, it was a match, Holes said.

“We knew then we had a serial rapist,” he said.

In 2006, Contra Costa prosecutors filed a John Doe complaint with a specific DNA profile of the NorCal Rapist, and a $500,000 arrest warrant was issued with that information, even though they didn’t yet know the identity, District Attorney Diana Becton said.

Sacramento police Detective Avis Beery described the suspect’s typical methods in carrying out the rapes.

He would enter houses late at night when the women were often asleep. He would overcome them, bind them and repeatedly sexually assault them, Beery said. He would ransack the houses, sometimes stealing items. Other times, he would kidnap the women and take them to an ATM where he would force them to withdraw money that he would steal, Beery said.

“The suspect was a real life boogeyman,” Yolo County District Attorney Jeff Reisig said.

Four victims have been reported in Yolo County — a Woodland woman in 1996, two women in Davis in 1997, and another woman in Davis in 2000, authorities said. The first-known victim, in Rohnert Park, spoke to NBC Bay Area on Friday afternoon.

“I finally see a face and have a name, and you imagine all these years who this person is and how did they know you and where did they come from,” said the woman. “I don’t think it’s hit me quite yet. It will.”

Public records show Waller had previous addresses in Richmond, El Sobrante, El Cerrito, San Pablo, and Rodeo in Contra Costa County; Nice and Lakeport in Lake County; and Sacramento.

Nobody answered the door Friday at Waller’s two-story beige home in a middle-class neighborhood in Benicia, according to the Sacramento Bee. Neighbors said Waller mostly kept to himself and would often work on his cars and water his tomato plants.

Students at Cal said they were notified in a campus-wide email Friday.

Sophomore Stephanie Gutierrez said it was “really, really scary “ to learn a long-term university employee is accused of being a serial rapist. She said Cal should put “all the resources it needs” to make sure Waller isn’t involved in any unsolved campus assaults.

The arrest comes nearly five months after authorities caught up to the Golden State Killer, a serial killer who raped more than 50 women across the state.

After that arrest revealed the groundbreaking genetic genealogy techniques, Holes was invited to speak about the process to Sacramento law enforcement.

“The NorCal Rapist was brought up as the No. 1 priority at the time,” Holes said.

Genetic genealogist Barbara Rae-Venter, who helped crack the Golden State Killer case, trained some of the Sacramento District Attorney investigators who pieced together family trees in the NorCal Rapist case.

She said if the public wants to see more cases solved, they should consider uploading their own genetic information to GEDmatch or those types of websites.

“Increasing the number of people in the database will not only help catch criminals but also will help in identifying the thousands of unidentified victims of violent crimes,” Rae-Venter said. “It is especially important for folks from minority groups to test as they are woefully under-represented in GEDmatch.”

Nate Gartrell contributed to this report.