Joseph James DeAngelo, accused this week of being the notorious East Area Rapist,took a terrorizing swing through the Bay Area in 1978 and 1979, according to authorities.

DeAngelo, 72, was arrested Tuesday in Sacramento by investigators who believe he committed at least 12 murders and 45 rapes over a 10-year period starting in 1976. In the first two years of his alleged crime spree, he is suspected of committing at least 39 sexual assaults in the greater Sacramento area and other parts of the Central Valley.

As the incidents stacked up, authorities became increasingly concerned that the East Area Rapist would turn his attention in a new direction. In August 1978, Sacramento County sheriff’s officials traveled to Contra Costa County to warn law enforcement.

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The arrest of Joseph DeAngelo in connection with the East Area Rapist and Golden State Killer cases.

Media: San Francisco Chronicle

Larry Crompton, a former deputy in Contra Costa County’s crime lab, recalls the meeting at which he and his colleagues were warned. At that time, few were aware of the extent of the East Area Rapist’s crimes.

“They said, ‘We feel he will be coming to your area,’” said Crompton, who is now retired and living in Oregon. “At that time we thought, ‘Why would he come to our area?’”

Within two months, the East Area Rapist had made his move.

On Oct. 7, 1978, DeAngelo allegedly raped a woman in Concord. Six days later, police say, he was in Concord again, where they say he gagged a 29-year-old woman and her husband and locked their 8-year-old child in the bathroom while he raped the woman. DeAngelo was then a police officer in Auburn (Placer County).

Later that month, on Oct. 28, the East Area Rapist reportedly went to San Ramon and raped a 23-year-old woman in her home.

The man raped again a week later in San Jose, police said, and a month after that an intruder pried open a sliding glass door at Heidi and Clark Tojo’s home in San Jose and raped Heidi Tojo, Crompton wrote in “Sudden Terror,” a book about the East Area Rapist.

The man forced Heidi Tojo to tie her husband’s hands tightly behind his back before raping her, Crompton wrote. Throughout the assault, the attacker threatened to shoot the victims.

Within a week, the East Area Rapist was in Danville.A woman who had fallen asleep reading poetry at her house awoke to discover a man wearing a ski mask who demanded money and food before he raped her, Crompton wrote. The man reportedly wore a ski mask and blue windbreaker.

Another sexual assault linked to the spree occurred in San Ramon 10 days later, authorities said.

On April 4, 1979, the East Area Rapist struck again, entering a home in the Mission San Jose area of Fremont. He tied up a woman’s boyfriend before raping her at gunpoint, The Chronicle reported at the time.

“The rapist tied up the boyfriend in a prone position, then placed dishes on the man’s back as a crude alarm system,” the story said.

The attacker apparently moved on to Walnut Creek two months later, targeting a 17-year-old babysitter. And nine days after that, he entered a home outside Danville through an open window and “threatened the house occupants before raping the woman,” The Chronicle reported.

Two weeks later in Walnut Creek, a man believed to be the East Area Rapist attacked a 13-year-old girl in the Rancho San Miguel neighborhood. On Wednesday, 39 years after the attack, that woman told the San Jose Mercury News that the suspect had held a knife to her throat.

On July 12, 1979, Danville saw the last of the East Area Rapist’s known crimes in the Bay Area,an attempted sexual assault.

The incidents created widespread fear. A Chronicle article from Oct. 19, 1978, noted that Concord’s police chief had warned residents to arm themselves. He also stoked controversy when he told girls at a junior high school to stop wearing “provocative clothing.”

DeAngelo was fired from the Auburn Police Department in the summer of 1979, and investigators believe he moved to Southern California and commited a series of killings and sexual assaults that drew national attention — and were later linked to the spree up north.

It’s unclear whether any of the Bay Area cases will result in charges.

Sean Webby, a spokesman for the Santa Clara County district attorney’s office, said no charges can be filed in the two San Jose cases because the statute of limitations has passed. Scott Alonso, a spokesman for the Contra Costa County district attorney’s office, said his office is evaluating the same issue.

“We’re working with the local law enforcement cases in the nine cases, and so far no cases have been filed,” Alonso said.

Sophie Haigney and Jenna Lyons are San Francisco Chronicle staff writers. Email: sophie.haigney@sfchronicle.com, jlyons@sfchronicle.com Twitter: @SophieHaigney @JennaJourno