Investigators looking into the case of the “Golden State Killer”, who is believed responsible for 12 murders and 51 rapes carried out throughout California during the ’70’s and ’80’s, have had a major breakthrough after DNA testing helped lead to the identification of a potential suspect.

Joseph James DeAngelo Jr, 72, was taken into custody by the Sacramento County Sheriff’s Department on Tuesday night on two murder charges for the 1978 deaths of Brian Maggiore and his wife Katie, who are believed to be the Golden State Killer’s first murder victims.

He was later also charged with the murders of Lyman and Charlene Smith who were found dead in their home by their 12-year-old son in 1980.

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.

Police say a DNA match in the past six days linked him to both crime scenes, but authorities refused to reveal what led to DeAngelo.

DeAngelo Jr has been charged by prosecutors in Sacramento, Ventura and Orange counties with eight counts of murder. He is being held without bail. The arrest took the former cop by surprise.

On Tuesday afternoon, in what Sacramento Sheriff Scott Jones called a “perfectly executed arrest,” FBI agents and detectives took DeAngelo into custody when he stepped outside his home.

“He was very surprised,” an elated Jones said Wednesday at a news conference outside the Sacramento District Attorney’s Crime Lab that helped lead to the arrest. “It looked as though he might have been searching his mind to execute a particular plan he may have had in mind…

“He was not given the opportunity. It happened almost instantaneously and he was taken into custody without any incident at all.”

It turns out that DeAngelo’s crimes inspired the state DNA-collection rules that appear to have identified him as the suspected killer.

The last known crime associated with the Original Night Stalker took place in 1986, but his notoriety persists. In 2004, California voters passed an initiative, bankrolled by the brother of one of his victims, that mandates collection of DNA samples from people convicted — or even arrested — in felony cases.

By 1978, the man had attacked victims in Oakland, Danville and Walnut Creek. In 1979, he killed two in Goleta, and two years later killed yet another couple in the Santa Barbara County town. Authorities in 2011 pinpointed DNA evidence from the killer in the 1981 slayings of Cheri Domingo, 35, and Gregory Sanchez, 27. And they matched that evidence with DNA from other crime scenes.

This is not DeAngelo’s first brush with the law, either.

DeAngelo previously worked as a police officer in Auburn, California before he was fired in 1979 for shoplifting a hammer and dog repellent from a Sacramento drug store. He was also a police officer in Exeter, California from about 1973 to 1976.

Investigators believe he was committing the crimes while he was an officer.

…’We knew we were looking for a needle in a haystack, but we also knew that needle was there,’ Sacramento County District Attorney Anne Marie Schubert said. ‘We found the needle in the haystack and it was right here in Sacramento. The answer was always going to be in the DNA.’

It turns out April 25th is National DNA Day. How fitting that it is on this day that a notorious serial killer may have been caught using it.