Golden State Killer suspect Joseph James DeAngelo was “very surprised” when he was arrested outside his Citrus Heights home Tuesday, police said.

Sacramento County Sheriff Scott Jones said that before the former police officer was taken into custody at 5 p.m. on April 24 they “developed a plan” to wait for him to come outside.

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“And so when he came out of his residence we had a team in place that was able to take him into custody,” Jones said at a Wednesday afternoon press conference. “He was very surprised by that. It looked as though he was searching his mind to execute a particular plan he had in mind… but he was not given the opportunity.”

DeAngelo, 72, worked as a police officer with the Exeter and Auburn police departments from 1973 to 1979. He was fired from the Auburn Police Department for allegedly shoplifting dog repellant and a hammer in 1979.

“Very possibly he was committing crimes during the time he was employed as a peace officer and obviously we are looking into whether he was on the job,” Jones said.

Image zoom Golden State Killer suspect Joseph James DeAngelo Sacramento County Sheriff's Office

DeAngelo is charged with capital murder in four killings: The February 2, 1978 slayings of Brian and Katie Maggiore in the Sacramento area, and the March 1980 slayings of Lyman and Charlene Smith in Ventura County.

RELATED VIDEO: Golden State Killer’ Suspect Identified as 72-Year-Old Ex-Cop Who Was Fired For Allegedly Stealing

But police say they believe he killed many more people. Over a 10-year-period — from 1976 to 1986 — the Golden State Killer was linked by DNA and method to 12 murders, 45 sexual assaults and more than 120 burglaries from Sacramento to Southern California’s Orange County.

Over the years, the man believed to be responsible for the alleged murder spree has also been known as the East Area Rapist and the Original Night Stalker.

Image zoom Brian Maggiore during his time on the police force FBI

Neighbor Kevin Tapia says DeAngelo mostly kept to himself but had shown odd behavior in the past.

“He would yell a fair amount at people, at his daughters, and he would yell at himself,” Tapia tells PEOPLE. “It was very odd. All of a sudden he would just start screaming and curse words.”

Tapia says DeAngelo yelled at him once when he was a kid. “He thought I threw something over the fence at him and he came out and yelled at me and wanted to speak to my Dad and they got in a verbal altercation,” he says.

“When he was younger, 15 or 20 years ago, he was definitely more aggressive yelling at neighbors, being vocal outside, yelling at himself or his kids. More recently you never saw him or heard him.”

Image zoom Lyman and Charlene Smith Courtesy Smith Family

Tapia says DeAngelo “raised three girls by himself.” Police have said DeAngelo has adult children.

“I never ever saw a wife,” Tapia added. “I never knew what happened to her or heard stories about what happened to her.”

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Sacramento County District Attorney Anne Marie Schubert says DeAngelo was not identified through a tip but through “innovative DNA technology.”

“If it wasn’t for that DNA his name would never have surfaced period,” she tells PEOPLE. “There was a needle in that haystack and we found that dam needle. I always believed it was a matter of persistence.”

Adding: “I always believed the answer was in Sacramento. I didn’t know the guy was living in Sacramento. That is just surreal. Living right here in the very community. It is crazy.”

• For more on the Golden State Killer, watch People Magazine Investigates: Golden State Killer Caught, airing Friday, April 27 at 10 p.m. and Sunday, April 29 at 8 p.m. on Investigation Discovery

According to jail records, DeAngelo is being held at the Sacramento County Mail Jail. He is 5-feet-11 inches and weighs 205 lbs., according to the records.

The attacks attributed to the Golden State Killer began in Sacramento in 1976 with the June 18 rape of a woman in the Rancho Cordova-Carmichael neighborhood.

The attacker wore a ski mask and would pry open windows and doors of homes of single women or couples. Once inside, he would enter the bedroom and shine a flashlight into his victims’ eyes.

After the arrest, Jane Carson Sandler, who survived a sexual assault by the killer, told PEOPLE, “I am speechless. Almost sick to my stomach because I am so excited. It is a dream come true.”