Authorities say at least 12 killed by 'Golden State Killer' across California

DNA helps cops identify northern California's "East Area Rapist" and southern California's "Original Night Stalker" as one man.
8:22 | 05/05/18

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Transcript for Authorities say at least 12 killed by 'Golden State Killer' across California
What makes the ones who do cross over? The daydreamer steps out of his trance and into a stranger's house. Every time the east area rapist strikes the police switchboard lights up. Hello Concord police department. We're getting an awful lot of calls. Some people turning in their neighbors thinking they might be the rapist. Reporter: It's the fall of 1977. Sacramento, California is under siege. A violent serial rapist is on the prowl. With this guy the next rape could be almost anywhere. This guy was a menace, he was striking time and time again. The fact they couldn't catch this guy just ignited the city in fear. Reporter: A lot of people are buying guns. Reporter: This spunky 13-year-old named Margaret Wardlow couldn't get enough of those headlines. It was really -- piqued my interest. Like, what was making this guy tick? Why was he doing this? Anything that she could read or hear about on TV of the east area rapist, she was just intrigued by it. Reporter: Thursday, November 10th. It's a school night and Margaret goes to bed early. I was awoken about 2:30 in the morning, with a flashlight in my face. And I knew at that moment, this is the east area rapist. Reporter: Margaret's mother tied up in the next room, the rapist stacking plates on her back. He did that with so many of the victims when there was more than one person in the house. Why would he stack the plates? So if he heard anybody moving, he was right back, and told them, "Don't move, don't move, I'm gonna kill you, I'll kill you." Like an alarm system. Yes. Like an alarm system. The whole time he'd been threatening me. He'd be saying do you want to die? And I answered him very clearly, saying, "I don't care." He said, "I'm going to kill you." And you told the serial rapist, "I don't care." I knew by telling him this, he most likely would leave sooner than later. He wasn't getting what he wanted. He wanted fear. He wanted to see fear in me. Margaret was probably the strongest young victim I have ever talked to. Reporter: She was victim number 27, but the attacks continue to escalate. Now spreading to the neighboring cities. Stockton, Modesto, Davis, Concord, San Ramon and two nights ago, freemont. Reporter: The east area rapist taunting his victims even further with chilling phone calls. Hello. I'm going to kill you kill you Whore. He would say things like, "Remember the fun we had." Sometimes it was just heavy breathing. But they knew it was him. How long after the fact would he make these calls? Sometimes it was within a week, and sometimes it was years later. So it was as if, as soon as a victim started to get comfortable, he would circle back and try to prolong the fear and suffering. He did everything he could to make sure that he tormented 'em for the rest of their life. The infamous masked man made his 44th attack. Our biggest problems are being able to clearly identify a suspect. What did he look like, as far as what the victims were saying? 5'10", 180. We thought he had lighter brown hair. The eye color was sometimes dark, sometimes light. Some said he had a strange smell. Did the victims give a description that was unique about him? Most of the victims described him as having a very small penis. Reporter: Detective Carol Daley says they thoroughly checked out all leads. There was not a stone left unturned in trying to identify this rapist. And we didn't have any luck there. Reporter: Authorities an canvassed neighborhood surveilling at all hours. They even brought out canines. All those resources, and yet, you still couldn't catch him. No, we didn't catch him. Reporter: There were few physical clues left behind but a blood sample showed the east area rapist had a rare genetic condition that would eliminate 85% of the population. They would bring a cloth out of a little kit and you would chew it so they would get your saliva. We went to ups briefings, and delivery people just volunteered. Our officers -- because at one time, everybody thought it could be a cop. Was there a point in time when there were clues that maybe he was former law enforcement or military? In attack number three. They're confronted with this man. He's got a mask on. He's got a t-shirt on. He's got a gun in one hand and a padded baton in another hand. And he says, "Freeze or I'll shoot." When you look at his tactics, he definitely had an understanding of how law enforcement would respond to this type of attack. He understood how law enforcement would investigate that. Well, he was definitely good at getting away with it. He was very good at getting away with it. Reporter: And there is something else striking the east area rapist reportedly said during one of his assaults -- a name. He is sobbing and saying, "I hate you, Bonnie. I hate you, Bonnie," over and over. What was the significance of that? That he had some significant female in his life named Bonnie. And he had some anger against what Bonnie had done to him. And he's taking that anger out on this victim that he's raping. The only thing we really know about the east area rapist is that he is a pro. He's been at this for four years now and still nobody even knows what he looks like. We felt that our next call was gonna be to a homicide. We really felt he was ready to kill. Reporter: Suddenly the spree of sex assaults seems to stop abruptly in 1979 with no rhyme or reason. What investigators didn't know was their biggest fear had come true. The rapist re-emerging in southern California, now a killer. It can happen to you. And apparently can happen without reason or motive. Reporter: Ten murders in succession earning him the nickname "Original night stalker." Among the victims, prominent attorney Lyman Smith and his wife Charlene. Daughter Jennifer was just 18 at the time. He was bigger than life. He loved to laugh. Charlene was vivacious, musical, loved to cook. She had a flair for style. They had been bludgeoned in the head with a log that had been collected from a wood pile outside the house. It was horrible. To think you're blindfolded, your hands are bound, they're behind your back. Charlene's body was processed for sexual assault evidence. And semen was found. Reporter: Police preserved that semen from Charlene Smith's rape kit. It would take 17 years to match the killer's DNA to the DNA collected at three other murder scenes. So they worked them independently for many, many, many years. It wasn't until the advent in the mid '90s of DNA that they were able to link the crimes. Reporter: Then four years later, in a stunning development, authorities are finally able to connect the original night stalker to the east area rapist. This serial offender is one of the most prolific in California, possibly in the United States. Your serial rapist in northern California was the same serial killer they were dealing with in southern California. How significant was that development? Holy smokes, this is like the big break. Because they got more insight, 50 cases worth of investigation, Reporter: Now they know the rapist and the killer are one man. A ten-year crime spree spanning 500 miles, at least 12 murders and 50 rapes investigators say. Now re-branded as the golden state killer.

This transcript has been automatically generated and may not be 100% accurate.

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