EXCLUSIVE: A sloppy digital footprint and DNA evidence led police to capture the BTK serial killer in 2005, decades after his first kill – and now that man says he sees "a clone of me" in last week's arrest of Rex Heuermann in connection with the Gilgo Beach murders in New York.

Heuermann, a 59-year-old architect and father of two who commuted by train from suburban Massapequa Park, New York, to Manhattan for years, hid in plain sight in a ramshackle home around the corner from the former Nassau County Police Academy.

Dennis Rader, also known as the BTK serial killer, laid out a series of similarities between the two cold case investigations.

"I was arrested age 59. Married, two kids," Rader wrote in a letter to Fox News Digital. "Husband, dad longtime a serial killer, stalker, used electronic devices, lives in a neighborhood undetected."

REX HEUERMANN'S WIFE PICTURED FOR FIRST TIME AS SHE FILES FOR DIVORCE FROM GILGO BEACH SERIAL SLAYING SUSPECT

Heuermann with open top butten, Rader in suit in split image

Gilgo Beach suspect Rex Heuermann, left, in an image prosecutors revealed in court documents. Serial killer Dennis Raider, right, also known as BTK, in court in 2005 after his arrest in 10 murders. (Suffolk County District Attorneys Office, REUTERS/Bo Rader/Pool FA)

Heuermann pleaded not guilty last week to six murder charges in the deaths of Melissa Barthelemy, 24, Megan Waterman, 22, and Amber Costello, 27. Police also suspect him in the death of Maureen Brainard-Barnes, 25, whose remains they found near the other three.

BTK and Heuermann were taken down similarly, Rader argued – "DNA and electronics his downfall much like me." The convicted killer claims he predicted the similarities years ago.

"I was correct," he wrote.

Heuermann standing in New York City.

Accused Gilgo Beach serial killer Rex Heuermann was captured on Google street view images months before his arrest in Midtown Manhattan. (Google Maps/Suffolk County Sheriff's Office)

Police arrested Rader in 2005 after years of cat-and-mouse games in which he taunted investigators and the media with messages, ultimately leading police to his doorstep with a trail of digital evidence. He had given himself the nickname "BTK" in reference to his preferred method of murder – "bind, torture, kill."

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Investigators from a Gilgo Beach task force created in early 2022 zeroed in on Heuermann after they linked data from his phone, numerous burner phones and the victims' phones to the suspect vehicle and cell towers near his home on Long Island and office in New York City.

Rex Heuermann's wife, Asa Ellerup and daughter, Victoria Heuermann walk on the street

Asa Ellerup, left, and her daughter Victoria Heuermann, right, leave a Best Buy store on Tuesday, July 18, 2023, the day before Ellerup filed for divorce from her husband, Rex Heuermann, who was charged last week with six counts of murder in the Gilgo Beach serial killings. (Dario Alequin for Fox News Digital )

Also like Rader, Heuermann's arrest shocked his family.

The lives of his wife and children were turned upside-down the night of his arrest, their lawyer, Bob Macedonio, told Fox News Digital.

Rader's wife filed for divorce almost immediately after his arrest in 2005. Heuermann's wife, Asa Ellerup, filed for divorce Wednesday.

GILGO BEACH MURDERS: THE INVESTIGATION IN PHOTOS

Gilgo beach sign on Ocean Parkway NY

A road sign directing drivers to Gilgo Beach off Ocean Parkway, about 45 miles east of New York City. (Michael Ruiz/Fox News)

"My first question when a long sought suspect in multiple murders is caught is, ‘does he have a family?’" said Kerri Rawson, Rader's daughter and an advocate for victims. "My family’s life was upended 18 years ago, February 2005, when we got the noon day knock and simple notification from the FBI, 'Your father is BTK.'"

Her father hid "in plain sight" for more than 30 years and committed 10 brutal murders, she said, including one around the corner from her childhood home.

WATCH: Former NYPD Inspector Paul Mauro visits scene where Gilgo Beach victims were found

Heuermann lived about a 25-minute drive from where the bodies were found in the brush north of Ocean Parkway – and there is evidence he could have gotten there just as quickly by boat as well.

Neighbors tell Fox News Digital that Heuermann was quiet and kept to himself. They mostly saw him during his morning commute, when he took the Long Island Rail Road to Manhattan, often in a three-piece suit and carrying a briefcase. Some said he creeped them out, and they avoided him.

Split image showing the Gilgo Four victims

Clockwise from top left, Amber Lynn Costello, 27, Maureen Brainard-Barnes, 25, Megan Waterman, 22 and Melissa Barthelemy, 24, disappeared after meeting with a client on Craigslist. The remains of the women were found in December 2010 at Gilgo Beach on Long Island. (Suffolk County Police Department)

Rader worked for years as a compliance officer, boasting to Fox News Digital that he had handed out more than 350 citations and other complaints before his arrest.

"From my own long experience and my own family’s, I ask [Heuermann's wife and children] be treated with dignity and respect, granted privacy and time to begin to wrap their heads and hearts around what is unfolding," Rawson told Fox News Digital.

A general view of Gilgo Beach

A skull mask mounted on a cross in the marsh behind Gilgo Beach, south of Long Island, New York, on Wednesday, July 19, 2023. The remains of four missing women were discovered in the brush near the beach in 2010. (Mega for Fox News Digital )

Rader will spend the rest of his life behind bars. He admitted to 10 slayings after his arrest in 2005 – but police are now investigating him in connection with two cold cases.

One is the disappearance of Cynthia "Cyndi" Dawn Kinney, a 16-year-old who was last seen leaving her job at her aunt and uncle's laundromat on June 23, 1976, in Osage, Oklahoma. The other is the abduction and murder of Shawna Garber, 53, on Halloween in 1990.

BTK leaves his arraignment, inset are photos of cold case victims Cynthia Dawn Kinney and Shawna Garber

BTK killer Dennis Rader is led from a Sedgwick County, Kansas courtroom after his arraignment on 10 counts of murder, May 3, 2005. The 60-year-old former Boy Scout leader is the "bind, torture and kill" murderer who terrorized Kansas for more than three decades. Inset are a portrait of Cynthia Dawn Kinney and an artist's rendition of what Shawna Garber may have looked like at the time she died. (REUTERS/POOL/Bo Rader-The Wichita Eagle, National Missing and Unidentified Person System, MacDonald County Sheriff's Office)

Rader has denied involvement in both cases.

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Police in South Carolina, Nevada and New York are all looking into whether Heuermann may be connected to other unsolved cases.

He currently faces six murder charges for the deaths of three women and is the prime suspect in the killing of a fourth whose body police found in roughly the same spot.

He is due back in court Aug. 1 and faces up to life imprisonment without the possibility of parole if convicted.