Ted Bundy is known as one of the most notorious serial killers in American history, having admitted to killing 36 women, but possibly having as many as 100 victims during his murdering spree in the 1970s.

After being given death sentences in 1979 and 1980, Bundy was on death row when murders started happening in Washington state in 1982.

Investigators were stumped by the slayings around south King County, as young women kept disappearing and with their bodies turning up along the Green River.

The murderer on the loose became known as the Green River Killer, but officials couldn’t track down his whereabouts — until they were offered assistance from none other than Bundy, who gave them insight into the mentality of a serial killer.

Eventually, with Bundy's help, Gary Ridgway was caught and admitted to his 49th murder on February 18, 2011, with actual estimates being closer to 80 victims.

Bundy and Ridgway both had Washington upbringings

Born on November 24, 1946, in Burlington, Vermont, Bundy moved to Tacoma, Washington, as a child — and grew up in the area, showing a fascination with knives at the age of three and an obsession with spying and stealing as a teen.

He graduated with a psychology degree from the University of Washington in 1972 and around 1974, women in the Washington and Oregon area started going missing. The word on the street was that they would be lured into a car by a man named Ted who pretended to be injured with his arm in a sling, needing their help.

Bundy later moved to Utah for law school, where he was caught. He eventually escaped from prison and ended up in Tallahassee, Florida — continuing to kill wherever he went.

Ironically Ridgway was born in Utah on February 18, 1949, but also raised in Washington state, near Seattle’s SeaTac airport. Before graduating high school, he joined the Navy and was sent to Vietnam.

When he returned, he started painting trucks — and around 1982, runaways and prostitutes started disappearing off of State Route 99 in Washington's King County. He tended to bring them to his home, strangle them and then dispose of their bodies in the woods, which is how several ended washing up along the nearby Green River.

READ MORE: Inside Ted Bundy's Troubled and Disturbing Childhood

Gary Ridgway prepares to leave the courtroom where he was sentenced to 48 life sentences without the possibility of parole on December 18, 2003, in Seattle, Washington. Photo: Josh Trujillo-Pool/Getty Images

Bundy offered his assistance from death row

By 1986, a detective named Dave Reichert had been working on the Green River case for years. Despite 40 female victims, he still didn’t have any reliable leads, when he got a fascinating offer to help.

“Don't ask me why I believe I'm an expert in this area, just accept that I am and we'll start from there,” Bundy wrote to Reichert from a Florida jail, where he was on death row. Bundy had been reading about the Green River Killer and saw Reichert’s photo in stories, according to the New York Times.

At the time, Bundy had already been imprisoned for six years and was waiting for this death sentence.

Reichert flew to Florida with fellow investigator Robert Keppel, who was an investigator on Bundy’s case. According to Keppel's book, The Riverman: Ted Bundy and I Hunt for the Green River Killer, he says that Bundy had reached out to him — and that he was the only one the convicted killer would talk to.

Some reports say that at some point, Bundy suggested that the Green River Killer — who he called “Riverman” — might be going back to the sites he left the bodies and performing sexual acts and suggested that the detectives stake out fresh burial sites.

“The sheriff [Reichert], who spent three days interviewing Mr. Ridgway alone, said he quickly realized that serial killers have a lot in common, whether they kill prostitutes, as Mr. Ridgway and Jack the Ripper did, young boys, as John Wayne Gacy did, or young women, as Mr. Bundy did,” the New York Times story said. “Both Mr. Bundy, who was put to death for the murder of three women and had confessed to killing at least 16 others, and Mr. Ridgway were sexual predators who killed during or after sexually assaulting or having sex with their victims.”

READ MORE: How Ted Bundy’s Education Facilitated His Career as a Serial Killer

Investigators felt both killers had 'no remorse'

The information that Bundy provided helped the investigators get inside the mind of a killer — especially one who knew the Washington area well — and eventually they did capture Ridgway in 2001.

“First off, there's no remorse,” Reichert told the New York Times of the serial killer mindset. “He doesn't have any feelings toward anybody, his family included. And that's what I saw in Bundy and what I saw in Ridgway.”

Reichert also said that Bundy would tell him actions he expected Ridgway to do, but in reality, they were veiled confessions of things Bundy had already performed. “It was as if Mr. Bundy was jealous of the attention the Green River killer was getting,” Reichert hypothesized.

Both killers also were proud of their actions. As the Times continued: “Like Mr. Bundy, Sheriff Reichert said, Mr. Ridgway craved attention and control and was prideful when discussing his killings. When detectives presented him with an unsolved murder to see if he would confess it, he told them: ‘Why, if it isn't mine? Because I have pride in...what I do. I don't wanna take it from anybody else.’”

Bundy died in an execution chair nicknamed Old Sparky on January 24, 1989, at the Florida State Prison, as crowds cheered outside. Ridgway was sentenced to life in prison in 2003, having reportedly committed more murders than any serial killer in U.S. history.