An Avalanche of evidence was hiding in plain sight.

The distinctive dark-green Chevrolet Avalanche that only recently led cops to suspect Rex Heuermann of the Gilgo Beach murders was long visible to neighbors, passersby — and even users of online street mapping sites.

Court documents obtained by The Post Friday detailed how investigators first focused on Heuermann just last year, after a vehicle-registration search showed the local dad of two owned a first-generation model of the truck that had previously been tied to the then-unknown killer.

It is unclear why it took so long for authorities to apparently make the link between Heuermann and the car, given that the architect seemed to make no effort to hide it. 

Archived Google Map street views even showed it regularly parked outside his ramshackle home in Massapequa Park, about 15 minutes away from where the bodies were found.

The Suffolk County District Attorney’s Office confirmed to The Post on Monday that the detail about a dark-green Avalanche being linked to the case came in soon after the bodies of the “Gilgo Four” were found strewn around Ocean Parkway in December 2010.

“That tip came in very early on in the investigation,” a rep with the DA’s office said.

The crucial vehicle information surfaced before detectives even had a profile of the serial killer.

“In regard to having an actual description” of the suspect, “we didn’t have that at the time,” Suffolk County Police Commissioner Rodney Harrison told Pix 11 on Monday of the early days of the manhunt.

“But was the vehicle something that we were aware of? Yes, that’s accurate,” the top cop said of an early tip about the same type of vehicle.

Harrison did not explain why it apparently took so long to start looking at the local Avalanche owner. Suffolk County Police did not immediately comment to The Post on Monday about the seeming delay.

Who were the Gilgo Beach victims?

Suspected serial killer Rex Heuermann — a New York City architect and married dad of two — was arrested in connection with the long-unsolved Gilgo Beach murders. The arrest is tied to the so-called “Gilgo Four,” women found wrapped in burlap within days of each other in late 2010.

The years-long investigation that led to the arrest revolved around the discovery of more than 10 sets of human remains along Ocean Parkway near Gilgo Beach in Suffolk County between December 2010 and April 2011.

Most victims were petite female sex workers with green or hazel eyes. But there were also two exceptions: a 2-year-old girl and a young Asian man.

Melissa Barthelemy, 24

• Barthelemy was a sex worker who lived in the Unionport section of the Bronx and dreamed of one day opening her own beauty salon. She was last seen alive in her basement apartment on Underhill Avenue on July 12, 2009. Heuermann was charged for Barthelemy’s murder in July 2023.

Maureen Brainard-Barnes, 25

• Brainard-Barnes was living in Norwich, Connecticut. She went missing after taking an Amtrak train from New London, Connecticut, to Grand Central Terminal in Manhattan on July 6, 2007. Her remains were found in December 2010. Heuermann was charged for Brainard-Barnes’ murder in January 2024.

Amber Lynn Costello, 27

• Costello, 27, was a sex worker and heroin addict who lived in West Babylon, New York, at a home with a woman and two men. She advertised on Craigslist and Backpage to support her and her roommates’ drug habits. Costello was found on December 13, 2010, after having been last seen leaving her home September 2, 2010. Heuermann was charged for Costello’s murder in July 2023.

Megan Waterman, 22

• Waterman, a 22-year-old mom of one, was last seen on June 6, 2010. She lived in Scarborough, Maine, and earned a living as an escort. She was last seen by her family boarding a New York-bound Concord Trailways bus in Maine. Her body was found on December 13, 2010, on the north side of Ocean Parkway, near Gilgo Beach. Heuermann was charged for Waterman’s murder in July 2023.

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Jessica Taylor, 20

• Remains belonging to Jessica Taylor, a 20-year-old woman working as an escort in New York City, were found in a wooded area in Manorville on July 26, 2003. Her additional remains — initially labeled “Jane Doe No. 5” — were discovered on March 29, 2011, along Ocean Parkway.

Valerie Mack, 24

• Valerie Mack was 24 years old and living in Philadelphia when she went missing. She worked as an escort, using the alias “Melissa Taylor.” Relatives last saw Mack in the spring or summer of 2000 in Port Republic, New Jersey, but she was never reported as missing to the police. Her partial skeletal remains were found in Manorville in September 2000 but were initially known as “Jane Doe No. 6.” More bones were found on April 4, 2011, along Ocean Parkway.

Unidentified Asian man

• The skeletal remains of a yet-to-be-identified Asian man were found along Ocean Parkway on April 4, 2011. It is estimated that the man was between 17 and 23 years old at the time of his death. He was approximately 5 feet 6 inches tall with bad teeth.

‘Peaches’ and her daughter

• An African American woman’s partial remains were discovered in Hempstead Lake State Park back in 1997, and she had become known as “Peaches” because of a bitten tattoo of a peach on her left breast. On April 4, 2011, police uncovered the remains of a toddler, who was about 2 years old at the time of her death. DNA testing confirmed that one of the skeletons was that of the 2-year-old girl’s mother, “Peaches.”

Karen Vergata

• A victim previously referred to as Jane Doe No. 7 has been identified as 34-year-old Manhattan woman Karen Vergata. Vergata is believed to have disappeared around Feb. 14, 1996; two months later, her legs were found in a plastic bag at a park near Fire Island’s Blue Point Beach. At the time of her disappearance, Vergata was believed to have been working as an escort. Two sets of Vergata’s remains were identified in August 2023.

Shannan Gilbert, 23

• Gilbert was a Craigslist escort who lived in Jersey City, traveled with her driver Michael Pak from Manhattan to meet a client, Joseph Brewer, at his home in the Oak Beach Association on the morning of May 1, 2010. She spoke with two neighbors before disappearing. Her body was discovered in a marsh near Oak Beach — about half a mile from where she was last seen alive — on December 13, 2011.

Jessica Taylor, 20

• Taylor, a 20-year-old woman working as an escort in New York City, were found in a wooded area in Manorville on July 26, 2003. Her additional remains — initially labeled “Jane Doe No. 5” — were discovered on March 29, 2011, along Ocean Parkway.

Sandra Costilla

• Costilla was murdered in 1993 but had not been included among the so-called Gilgo Beach victims — until now. Investigators suspected convicted serial killer John Bittrolff in Costilla’s death, but he was never charged in her slaying — which remains one of several unsolved Long Island murders.

Heuermann, 59, still had his Avalanche when he was arrested Thursday, and it is one of the items taken as part of a mountain of potential evidence.

Google Map images from as early as 2011 – the year after the murder investigation into the so-called “Gilgo Four” was launched – show it parked both on the street and in the driveway.

Still, court documents reveal that it was not until March 14, 2022, “approximately two months into [a] renewed joint investigation,” that the local dad’s name emerged as a registered owner “of a first-generation Chevrolet Avalanche … at the time of these murders.

“This was significant, because a witness to the disappearance of [murder victim] Amber Costello identified a first-generation Chevrolet Avalanche as the vehicle believed to have been driven by her killer,” a bail application said.

Investigators then got more information during follow-up interviews last year with the key witness, whom Harrison had earlier identified as Costello’s pimp who’d seen the Avalanche at the sex worker’s West Babylon home.

“We reinterviewed the individual who kind of gave us a better description of Rex Heuermann — saying pretty much that he had bushy hair, these big glasses and was the size of an ‘ogre,'” Harrison told Pix 11.

Court papers also described the pickup-driving john as looking “like an ‘ogre’” and about 6-foot-4 tall — which “mirrors the physical attributes” of Heuermann, who is that exact height.

“And that really helped us get this case going in the right direction,” Harrison said of the suspect’s arrest last Thursday.

The pimp told cops he saw the suspect and his Avalanche while planning a September 2010 “ruse” to scare off Costello’s john by pretending to be an angry boyfriend, so they could keep the cash without sex.

Instead, the angry john demanded they meet the next night — with the burner phone he used linked to Massapequa Park, where the architect lived just miles from where Costello and the other so-called “Gilgo Four” women’s bodies were found months later in 2010.

That night would be the last time Costello, 27, was seen alive — leaving her house at the same time as a witness saw “a dark-colored truck” drive by.

Heuermann was arrested outside his midtown Manhattan office Thursday and charged with murdering Costello, Melissa Barthelemy, 24, and Megan Waterman, 22.

He was also named the prime suspect in the death of Maureen Brainard-Barnes, 25.

Heuermann pleaded not guilty Friday.