New York prosecutors are "pleased" the suspect in the Gilgo Beach murders appeared surprised by his arrest in connection to the gruesome Long Island slayings after authorities accelerated the case to maintain secrecy.
Suffolk County District Attorney Ray Tierney said he believes Rex Heuermann did not expect to be taken into custody in Manhattan last week despite allegedly closely monitoring the investigation on the internet.
"I think he was extremely surprised," Tierney told "America's Newsroom" Monday. "I think we utilized the grand jury because we wanted to maintain investigative secrecy. We were concerned about that all along."
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"We actually took the case down a little bit earlier than we had planned because we were worried about that in part, so to see how surprised he was really made us pleased that we were able to maintain that secrecy," he continued.
Heuermann, a 59-year-old married father of two and an architect working in Manhattan, allegedly killed three of the four women known as the "Gilgo Beach 4," back in 2010, and he's the prime suspect in the fourth woman's death.
Tierney said Heuermann was closely monitoring the investigation through Google searches, which prompted officials to do what they could to keep the details of their progress discreet.
"We have maintained our secrecy because we were afraid that this one person, this killer, would be trying to monitor our… investigation through the internet, and once we got his Google searches, we saw that that was certainly the case," Tierney said.
"He was asking questions such as… 'What is the phone evidence in the Gilgo case? How… come they can't trace the phones in the Google case?' So he's asking specific questions with regard to our investigative means," Tierney said.
"He was also making searches of the victims, looking at pictures of the victims online, and he was running searches of the victims' siblings and in one instance admitted that he was the killer," he continued. "He had some disparaging things to say about the sister and said he was going to come find her."
But one of the critical components leading to the breakthrough had to do with zeroing in on his truck and a physical description tip officials received from a witness last year.
"The witnesses that indicated that this person that they described as a very large individual was with Amber Costello shortly before she disappeared and that he was driving this avalanche vehicle," Tierney said. "But it wasn't until March 14th of 2022 that we were able to link an avalanche vehicle to Rex Heuermann, who matched that unique physical description."
Police also previously stated they were able to link Heuermann to the murders after they obtained DNA evidence from a pizza he ate.
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"We have hairs which were recovered from Megan Waterman… and a hair that was recovered from the last victim, Amber Costello," Tierney said. "The DNA profile from the two hairs recovered from Waterman matched one hair matched to the DNA profile of Heuermann. The other one matched the DNA profile of his wife. The hair found on Amber Costello, that profile matched his wife."
But the evidence against Heuermann doesn't stop there – officials were also able to gather phone evidence linking him to the gruesome killings.
He purportedly used burner phones, and New York authorities were able to use a perimeter of cell phone ping locations that matched calls made to some of the victims, according to the UK Guardian.
"Back in 2012, when a lot of this material was still available, there was an FBI phone expert who went into and drove through the Massapequa Park area and established a map of the phone, the phones, the cell phone coverage in that area, and he indicated that he showed a small area in this Massapequa Park neighborhood, which indicated that not only was the killer using a phone in that area, but one of the victims had used her phone in that area as well," Tierney said.
"Similarly, they went to Midtown Manhattan, and they mapped out a same area in Midtown Manhattan. What's significant about that, of course, is the defendant lives in this small area in Massapequa Park and works in the area located in Midtown Manhattan."
Since Heuermann's arrest, officials have been searching his home in Massapequa Park, which is roughly a 25-minute drive from where 11 sets of human remains were located. Tierney said they belonged to nine women, one man, and one child.
Heuermann pleaded not guilty to the murders of Melissa Barthelemy, Megan Waterman and Amber Costello. He could face life behind bars without parole if convicted.
Tierney confirmed the investigation into the death of Maureen Brainard-Barnes is still ongoing, although Heuermann is the prime suspect.
Fox News' Chris Eberhart, Adam Sabes and Stephen Sorace contributed to this report.
