Suffolk County District Attorney Raymond Tierney revealed details about the investigation into the arrest of Rex Heuermann, 59, saying it involved more than 300 subpoenas and search warrants. 

"This case is not over; it's only beginning," Tierney told reporters Friday afternoon of the probe into the long-unsolved killings of women whose bodies were found on Long Island's Gilgo Beach more than a decade ago. "We're continuing to execute search warrants and anticipate getting more evidence."

In court Friday, Heuermann, of Massapequa Park, pleaded not guilty to three counts of first-degree murder and three counts of second-degree murder in the deaths of Melissa Barthelemy, Megan Waterman and Amber Costello, according to the indictment. Those three women, along with Maureen Brainard-Barnes, were all found in close proximity to one another in 2010 and have been called the "Gilgo Beach Four." 

Heuermann was ordered held without bail. His next court appearance is scheduled for August 1. 

In a bail application, prosecutors outlined how investigators re-examined old clues that led to the suspect and developed new evidence to close in on him after so many years. 

Tracking a suspected serial killer

In January 2022, a team of federal, state, and local investigators joined forces to launch the Gilgo Beach Homicide Investigation Task Force. According to the court documents, investigators began a "comprehensive review of every item of evidence" in the case.

The Avalanche and "the ogre"

About two months later, Heuermann, an architect, and married father of two, was first identified as a suspect. In March 2022, detectives linked Heuermann to a first-generation Chevrolet Avalanche pickup truck registered to him at the time of the murders, similar to one reported seen by a witness when one of the victims, Amber Costello, disappeared in 2010. 

Heuermann was described by the witness to police as appearing like an "ogre."

The pizza crust and a hair

According to the court documents, on or about Jan. 26, 2023, a surveillance team recovered a pizza box thrown by Heuermann into a garbage can on Fifth Avenue in Manhattan. The pizza box was sent to the Suffolk County Crime Laboratory for analysis. 

On April 28, 2023, a detective hand-delivered a portion of male hair that was found on Megan Waterman that had been preserved as evidence to the same lab where the pizza crust had been tested.  

According to the court filing, on or about June 12, 2023, the forensic lab compared the mitochondrial DNA from the pizza and the hair and determined that the "DNA profile(s) are the same" — specifically that 99.96% of the North American population would be excluded as matches to the hair. 

"It is significant that (Heuermann) cannot be excluded from the male hair recovered near the 'bottom of the burlap' utilized to restrain and transport Megan Waterman's naked and deceased body," prosecutors wrote. 

Retesting hair samples 

Authorities recovered hairs found with each of the victims, which were too degraded to test for DNA with the techniques available at that time. But the technology improved, Tierney said, and investigators were able to test the hairs with more advanced methods.

In July 2022, 11 bottles were collected from a trash can outside of the Heuermann home and sent for mitochondrial DNA testing. DNA profiles generated from the bottles were tested against previously tested hair samples recovered on the remains of Megan Waterman and Amber Costello. Results found that Heuermann's wife could not be excluded from either of the female hairs recovered on the remains of Waterman and Costello. The hair was believed to have been transferred from her husband's clothing. Heuermann's wife was out-of-state at the time of each of the murders, according to the court filing. She has not been charged.

Burner phones, selfies and Tinder

The investigation also turned up connections with burner cellphones and other phone data allegedly linked to the suspect. Tierney said FBI analysts were able to compare the cell site data of the victims' cellphones and data from seven prepaid, anonymous burner phones the suspect allegedly used to communicate with each of the victims. 

"Then, shortly after the death of the victim, he would get rid of the burner phone," Tierney told reporters.

According to the court documents, Heuermann used a burner cellphone to contact the three women.

Over the course of the investigation, investigators located a number of online accounts and burner phones linked to Heuermann, which were held by him in fictitious names and used for illicit activities, according to the court filing.

A search warrant conducted on a fictitious AOL Account revealed "selfie" photographs that appeared to have been taken by Heuermann of himself and sent to solicit and arrange for sexual activity. American Express records obtained via subpoena revealed recurring "Google Pay" payments made by Heuermann to the dating app "Tinder," which linked to a burner phone.

A review of call records for two additional burner cellphones revealed that both cellphones were used extensively between 2021 and 2023 for prostitution-related contacts.

On May 19, 2023, Heuermann was observed by law enforcement at a cellphone store in Midtown Manhattan, where they say he purchased additional minutes for a burner cellphone.

An arrest

Heuermann was arrested by Suffolk County Police Officers at his office in Manhattan on July 13, 2023.  At the time of his arrest, Heuermann was carrying a burner cellphone which was linked to a Thawk Email Account used to conduct the online searches, according to the court document.

Authorities say in a 14-month period, Heuermann had more than 200 Google searches on the Gilgo investigation and additional searches looking for photos of the victims and their family members.

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• Rex Heuermann
• Gilgo Beach Murders