An arraignment is scheduled Monday for a married university employee believed to be the so-called "NorCal Rapist," suspected in the sexual assaults of at least 10 women in crimes that began more than two decades ago.

Roy Charles Waller, 58, an employee at the University of California, Berkeley, who lives in Benicia, Calif., was arrested Thursday morning as he arrived for work. He is charged with 12 counts of forcible sexual assault, which on conviction could carry a life sentence, officials said.

"The answer has always been in the DNA," Sacramento County District Attorney Anne Marie Schubert said Friday at a news conference.

Roy Charles Waller, who is suspected of committing at least 10 rapes across Northern California between 1991 and 2006. Sacramento Police Department via AP

She said police identified Waller through the public genealogy website GEDMatch, and the genealogy was conducted in the 10 days before Waller’s arrest, but authorities did not detail a timeline.

That website was used to link the alleged suspect in the so-called “Golden State Killer” murders and rapes in California from 1974 to 1986. Former police officer Joseph James DeAngelo, 72, was arrested by Sacramento police in April.

"I've been waiting a really long time for this day to come," Sacramento police Det. Avis Beery, who has been involved in the NorCal rapist case for 12 years, said Friday. "I never gave up hope that this day would come."

Waller is charged in connection with two victims in Sacramento County, but he faces potential charges from five other counties, where sexual assaults that Sacramento Police Chief Daniel Hahn called “horrific” occurred over a 15-year-period ending in 2006. There are at least 10 victims that authorities know of, officials said.

None of the sexual assaults are believed to have occurred on the UC Berkeley campus, police and university officials said. UC Berkeley said in a statement that he worked in the college’s Environment, Health and Safety department. He was a safety specialist there related to the use of machinery and equipment, NBC Bay Area reported.

Sexual assaults occurred in Sonoma, Solano, Contra Costa, Yolo, Butte, and Sacramento counties, beginning in 1991 in Rohnert Park, authorities said.

"We have confirmed via DNA that Waller is the suspect in many of these crimes,” Hahn said.

A map marks where a series of rapes in Northern California occurred starting in 1991, is displayed during a news conference on Sept. 21, 2018, in Sacramento, California. Rich Pedroncelli / AP

Beery said the NorCal Rapist would break into his victims’ homes at night, sometimes when they were asleep, overpower them and ransack their homes—sometimes kidnapping them and forcing them to take money out of ATMs.

"He would overcome them. He would bind them, and then repeatedly sexually assault them," Beery said.

Waller is being held without bail, and an arraignment is scheduled for Monday, Schubert said. Online records do not list an attorney for him.

A woman who said she was Waller's stepsister but would not give her name when reached by phone Saturday said the allegations are "mind blowing" but she has not spoken to Waller in around eight years. She said Waller "always thought everyone was below him" but she never suspected he would be accused of the crimes for which he is charged and suspected.

Prosecutors in the other counties where investigators believe the NorCal Rapist struck will be reviewing their information for possible charges, Schubert said. In a sexual assault in Butte County, DNA was recovered after the victim stabbed the assailant in the arm, Butte County District Attorney Michael Ramsey said.

Contra Costa prosecutors filed a John Doe warrant 10 years after a 1996 attack on Halloween in the city of Martinez. The complaint was for a person “with the specific DNA profile of this individual,” said District Attorney Diana Becton.

Hahn, the Sacramento police chief, said the NorCal Rapist committed "horrific crimes where he terrorized women in jurisdictions throughout northern California, typically for hours at a time."

"There is one less dangerous predator on our streets this morning," he said Friday.

A woman who was sexually assaulted in her Rohnert Park condo in 1991 told NBC affiliate KCRA in Sacramento after Waller's arrest that when the district attorney's office called with the news, it was a shock.

"It's something I've been waiting for so very long, and so it doesn't feel quite real yet," she said. She said a man wearing a mask held a gun to her head and forced her into a bedroom and tied her up during the attack.

She told the station that if she had a chance to address the man who attacked her, she would say, "You didn’t ruin me."

"He's pathetic to me. I’m not afraid of him. I would tell him what he did, what he’s done to my life. The terror he caused me that night. It was terror," she said. "I didn’t think I was going to make it out alive."