Serial killer experts and FBI profilers speak to PEOPLE about what new details mean for the Long Island Serial Killer case

Nearly a dozen bodies — mostly of women — have been found around Gilgo Beach in New York. Are they connected? Subscribe to PEOPLE now for details of the Long Island Serial Killer, on newsstands now.

He’s the sort of killer who is often social and extremely good at making people feel comfortable. He grooms his victims before he strikes. He takes risks — and sadistic pleasure — in taunting his victim’s family and friends. He probably isn’t a substance abuser.

According to two experts, this is the emerging picture of whoever is responsible for at least some of the 10-plus dead bodies discovered around Long Island’s Gilgo Beach in New York.

The case has since been dubbed the Long Island Serial Killer. And though the investigation continues, with the help of federal authorities, no suspects have ever been named.

Questions abound: Is only one person responsible for all of the dead? How many victims are there? What connects them all?

There are clues as well — such as the ways in which some of the victims were killed, and how they were stalked before dying — and it’s these pieces of information that have shed some light on the possible killer or killers.

“What I would say is that when you are dealing with a serial killer, they tend to be very predatory individuals,” Mary Ellen O’Toole, the director of the forensic science program at George Mason University and a retired FBI agent and profiler, tells PEOPLE in this week’s issue, on newsstands now.

“They are hunting human beings,” O’Toole says. “The predatory behavior has to do with looking for women ultimately to murder.”

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Long Island killer victims
Suffolk County Police Department

The four dead escorts who were first discovered — Melissa Barthelemy, Maureen Brainard-Barnes, Megan Waterman and Amber Costello — were in contact with their killer through online ads as well as via cell phone before they disappeared.

O’Toole believes that was part of the killer’s grooming process.

“He contacts them and then he is in computer contact with them, he is manipulating them in three different ways, [and] that is a lot of work,” she says. “It is risky. One of these young women could become suspicious. That says a lot about him. This is part of his hunting behavior: that manipulation and the hunting process and his ability to control his women in his hunting process.”

“He hates women, obviously,” serial killer expert and criminal profiler John Kelly tells PEOPLE. “The phone is definitely his trolling weapon.”

Kelly, president of STALK Inc., says the killer is capable of hiding his darkest thoughts and making his victims feel comfortable in order to lure them in. “He’s such a good talker that he is able to find out if the girls are being watched over, if they have a pimp — he’s going to talk to make sure its safe to pick them up,” he says.

“He has probably talked to a lot of women that didn’t know he talked to them,” Kelly says. “If you look at the four girls, the specific four girls from Gilgo, they are not from New York City. They are from different areas, upstate New York and different states. They may not have the street smarts that a girl in New York City might have.”

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The killer also appears to take sick pleasure in taunting the victims’ friends and family. A friend of Brainard-Barnes’, the first of the victims to disappear, says she got an odd call a few days after the 25-year-old vanished in 2007. The man asked her if she knew “Marie” [Maureen’s escort name] from Connecticut.

“[The man] said she was at a whorehouse in Queens,” Sara Karnes tells PEOPLE. “I told him she would never go for that, because she was independent. He goes, ‘Well, that’s where I saw her.’ And he described her to a T to me.”

Karnes says the man seemed helpful at first, but when she asked him to call her back on an unblocked number he said he would but never did.

Karnes, who passed her information on to the police, says the man she spoke to didn’t have an accent.

“He definitely isn’t from New York, Boston or Maine, because those are the strongest places the accent comes out of,” she says. “But he accentuated his S’s and his T’s. He spoke properly.”

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After Barthelemy vanished in 2009, a series of calls came in after from her cell phone to her younger sister, Amanda.

“He was tormenting her,” Melissa’s mom, Lynn, tells PEOPLE. “He was very calm. The last call he said he had killed her.”

“When you start looking at taunting behavior attached to a serial murder case, it ratchets it up — you don’t see that with a lot of cases,” says O’Toole. “It puts you at much higher risk of being apprehended. It is an added interaction. He is getting some kind of sadistic pleasure out of it. It would be horrifying. … Even after death he is involved with them.”

Given the gaps in time between victims, Kelly believes the Long Island Serial Killer is probably not a substance abuser and can curb his murderous rages for long periods of time.

“Usually serial killers who use substances or are addicted to hunting and killing women, they cannot maintain a cooling off period for any period of time,” Kelly says. “[‘Green River Killer’] Gary Ridgway didn’t use substances. They have much much longer cooling off periods and are able to not act out because they don’t have this big uninhibitor in them.

“I don’t think this guy is an addict. These types of guys don’t kill every time out. ”

Kelly says the police can also tell a lot about the killer’s personality by how they disposed of their victims. Barthelemy, Brainard-Barnes, Costello and Waterman were discovered wrapped in burlap and found within about 500 feet of each other.

“The bodies being lined up could be his art,” Kelly says. “Usually serial killers focused on art [also] usually focus on posing their bodies. I know serial killers love to revisit the areas that they have dumped their bodies so he can relive the fantasy.”

A lot can be determined by the condition of the bodies at the scene, O’Toole says: “Were they all placed there at the same time or were they kept in one location?”

Long Island Serial Killer - News
Credit: Uli Seit/The New York Times/REDUX

‘More Than One Killer’?

While the foursome are likely linked, the connections between the other victims, which include a toddler and an Asian male, are more tenuous. They weren’t all killed the same way — some of them were dismembered and scattered at other locations in the beach area— and they don’t all match the same demographic profile.

“I think that there is a good possibility that there is more than one killer,” O’Toole says. “In this case, you have young women whose first contact is an online escort service, their remains are in a burlap bag along the sound, and their manner of death is strangulation.

“And then you have another set of victims that have been dismembered, and their remains have been found in the same area as well. The distinction between dismemberment and non- is significant.”

But Kelly disagrees. “It is very hard for me to believe that two serial killers could have found the same dump site,” he says.

“That is extremely rare they would both decide to dump bodies on the same patch of land or on the same highway. This guy could have started with one MO, and then for whatever reason decided that wasn’t safe anymore, and then decided to use a different means for this disposal.”

Whoever the killer or killers turn out to be, the victims’ family members and friends hope that they will live to find out.

“I want to pick his brain,” Costello’s sister, Kim Overstreet, tells PEOPLE in this week’s issue. “I want to know what she went through. I think my first question would be: Why did you pick my sister?”