The Nine Things That Make A Serial Killer

The accused Gilgo Beach murderer fits the chilling profile of a serial killer, according to criminal psychologist Rachel Toles who shared her insights with Newsweek.

Heuermann, who was first arrested in July 2023, stands accused of the brutal murders of six sex workers whose bodies were discovered along Long Island more than a decade ago.

“We often dismiss serial killers as bad seeds, born this way, psychopathic,” the host of the true-crime podcast Psychology of Serial Killers told Newsweek. “In all my research, I have yet to find one that was simply born this way. There are nine cumulative factors that make a serial killer.”

Toles explained that the criteria ranges from parental influence to bullying and head trauma.

These factors must align concurrently, making serial killers a rare phenomenon. She emphasized that not everyone who experiences one or two of these factors becomes a serial killer, underscoring the complexity of their formation.

The 60-year-old Heuermann first faced charges for the grisly murders of Melissa Barthelemy, Megan Waterman, Amber Lynn Costello, and Maureen Brainard-Barnes —infamously known as “The Gilgo Four.”

Their bodies, discovered in burlap sacks along New York’s Ocean Parkway over a decade ago, shocked the nation. Just last week, Heuermann’s potential victim list grew longer with fresh charges for the murders of Sandra Costilla and Jessica Taylor.

Genetics

Toles talked about how genetics have played into serial killers in different ways in the past.

“How big or small that is, we just don’t know,” Toles said. “We just know that there’s what people call aggressive, unfavorable genes that sometimes get activated in certain environments.”

She referenced Charles Whitman, who became known as the “Texas Tower Sniper,” had a brain tumor that was found during an autopsy.

On Aug. 1, 1966, Whitman used knives to kill his mother and his wife in their respective homes. He then went to the University of Texas at Austin with multiple firearms. He shot at people indiscriminately shooting, killing three people inside UT Austin’s main building. He then went to the observation deck and fired at random people for 96 minutes.

Austin Police Department patrolmen Houston McCoy and Ramiro Martinez shot and killed Whitman.

While nothing can be definitively said, the cancerous cells could have caused him to kill 17 victims, according to a psychiatric evaluation. Forensic investigators theorized that the tumor pressed against Whitman’s amygdala, which is related to fight-or-flight responses.

Toles said the brain tumor almost activated otherwise benign factors within Whitman’s head.

Mother

While not a lot about Heuermann’s mother, Dolores, is known, Toles does know she was a single mother and must have contributed to her son’s unstable upbringings.

“She is just a part of the cumulative factors,” Toles said. “I just don’t know how she played a role yet, but I can guarantee that Rex’s mother did something because his rage was directed at women.”

The hunt for the alleged Gilgo Beach serial killer started in 2010 when 11 sets of human remains were found in Suffolk County. The search first turned up the remains of Barthelemy, Waterman, Costello and Brainard-Barnes and Taylor. Valerie Mack, who was mentioned in recent court documents but has not been linked to Heuermann, was also in the area. All the women were sex workers in their mid-20s.

Toles said this was not simply because of Heuermann’s “sexual preference.”

This relates directly to Ted Bundy, a serial killer that was rejected by his mother. His maternal grandparents raised him so that social stigma wouldn’t hit the family since Bundy was born out of wedlock.

Bundy went on to become a serial killer who kidnapped and raped dozens of the young women he murdered during the 1970s. He confessed to 30 murders between 1974 and 1978.

While being transported from jail to a courthouse for a preliminary hearing, he visited the courthouse’s law library and escaped through a window. He was a fugitive for six days. He also later escaped through the ceiling of his jail later the same year. He committed additional homicides and assaults while on the run.

Bundy was executed in the electric chair on Jan. 24, 1989.

Father

For Heuermann, his father, Theodore, was a big factor in his serial killer upbringing, Toles said. While his dad died when Heuermann was just 11 years old, the now alleged Gilgo Beach murderer suffered from physical, emotional and potentially sexual abuse at the hands of his father, Toles said.

“He was extremely withdrawn, which is signs of abuse,” Toles said.

Toles said almost every sexual sadist serial killer has a link back to sexual abuse in some way. The issue, however, often goes under reported, particularly with boys.

Author Eric Hickey reported in 1997 that among a group of 62 male serial killers, 48% had been rejected as a child by a parent or some other important person in their lives.

“That’s a big one that we don’t talk about a lot, but it can be massive,” Toles said.

Toles calls these repressed issues “unresolved.”

For Jeffrey Dahmer, for example, he described his father, Lionel, as a “good father, as caring and concerned as any child would wish.” Even still, many experts including Toles do not believe this. Lionel and his first wife were accused of neglecting Dahmer during his childhood.

Dahmer went on to become the “Milwaukee Cannibal.” He murdered and dismembered 17 men between 1978 and 1991. Many of his later murders also involved cannibalism and necrophilia.

Dahmer was sentenced to 16 lives in prison. In 1994, he was beaten to death by another inmate at the Columbia Correctional Institution in Wisconsin.

Home Life

Bad upbringings have had a role in many serial killer’s backgrounds, including Brazilian Pedro Rodrigues Filho, who was also known as “Killer Lil’ Pedro.”

His skull had been bruised from his father kicking his mother’s pregnant belly during a fight. Rodrigues Filho claimed he first felt the urge to kill someone at 13 during a fight with his cousin.

As a teenager, he killed suspected criminals. He was officially sentenced for 71 murders. He served 34 years in prison prior to his release in 2007.

In 2011, Rodrigues Filho was in jail again for inciting riots. After a second release from prison, he said he was reformed and became a celebrated YouTuber. He was fatally shot in 2023 in a drive-by shooting.

The factor of home life can come into play in multiple ways, Toles said, including abuse.

“There was a lot of disfunction that was involved,” Toles said. “There were a lot of signs of this escalating.”

The home becomes an unsafe place for many, especially those who grew up to become serial killers.

They’re also taught the idea of externalization, Toles said. The blame is never on an individual, which is why many serial killers will go on to say their home life as a child was “perfectly fine.”

“They didn’t get a sense of accountability,” Toles said. “It was the world’s fault.”

Rex Heuermann’s brother, Craig, also went to jail, Toles said. As a young child, Rex Heuerman got in trouble for shoplifting too.

“When people cross boundaries like this, it is a complete confession that somebody early on crossed boundaries with them over and over,” Toles said.

Ages 3 to 5

There are two age ranges that seem to have great influence in a serial killer’s upbringing. The first is around the ages of three to five.

“There’s always a traumatic event that happens during this time,” Toles said.

This is also around the time when a paraphilia, or intense sexual obsession is formed Toles said.

“Every serial killer has one,” Toles said.

Enzo Yaksic, who runs the Atypical Homicide Research Group, told Newsweek Heuermann is a “prototypical sexual sadist.” Toles called this obsession a “splitting” of one’s psyche.

Dr. Robert Schug, a forensic psychologist and criminology professor, said the murders could suggest Heuermann’s sexual idealization was “spiraling out of control.”

“I’m wondering if and why murder became a problem-solving tool for him,” Schug told Newsweek. “The homicidal behavior is solving some function in their lives.”

Yet, Toles noted that majority of rapes go underreported. Somebody like Bobby Joe Long, a serial killer in Florida, would try to “get rid of the evidence” after he was caught for rape.

Long abducted, sexually assaulted and murdered at least eight women in the Tampa Bay area in Florida in 1984.

Forensic evidence included clothing, carpet fibers, semen, strangulation marks and rope knots. He was sentenced to death for two of the eight murders.

He was executed by lethal injection on May 23, 2019.

Brain injury

The criteria don’t necessarily happen in the exact same order for each case. Head traumas could come from a variety of incidents, such as in utero, if the baby is shaken, if the child is beaten or even sexually abused. They can also happen in adulthood.

Toles mentioned serial killer Gary Heidnik, who was often taunted as a child with phrases like “football head.”

Heidnik was a serial rapist who would kidnap and torture women. He raped six of them and murdered two while holding them captive in a self-dug pit in his basement in Philadelphia. He was sentenced to death and executed by lethal injection in 1999.

Heidnik later claimed he was emotionally abused by his father, returning to another of Toles’ criteria.

“But every single one of them has a brain injury of some kind,” Toles said. “It’s also often more than one (brain injury).”

Toles said Heuermann’s injuries are apparent from his face, which is “completely misshapen.” She believes he was hit at least once to his head, if not multiple times.

After Amber Costello, one of the original “Gilgo Four,” went missing, a witness told police a man, who is later thought to be Heuermann, looked like an “ogre.”

“I don’t like speaking ill of anyone,” Toles said. “But that was the first thing that struck me. I could hardly look at his photograph.”

Bullying

Charles Manson was apparently bullied by a teacher on his first day of school and ran home in tears. His uncle forced him to return to school the next day dressed as a little girl. At age 9, Manson set his school on fire. He was sent to a strict reform school, the Indiana Boys School, where other students allegedly raped Manson with encouragement from the staff.

Manson became a cult leader in California that committed a series of at least nine murders, including the actress, Sharon Tate.

Similar to Manson, Toles thinks this criterion was potentially the most influential in Heuermann’s serial killer development. No one stepped in to support him. A teacher once told students to stop, but that only diminished the physical abuse, Toles said she read about Heuermann.

Toles is also writing a book on what makes a mass shooter and has found similar links to bullying. About 20% of students said they were bullied at school during the 2019-20 year, according to a study conducted by the Pew Center for Research. Being made fun of or called names was the second most common form of bullying.

Even still, fewer than half, 46%, of middle and high schoolers who were bullied in the 2019-20 school year notified a teach or another adult about it.

“Bullying is across the board,” Toles said. “You’re just dousing them in gasoline and they’re already on fire.”

Toles said she has learned this creates both internalized and external trauma for Heuermann, from the abuse he suffered from his father to the taunts and fights from his own peers.

“He was just relentlessly picked on as a kid, from elementary all the way even through high school,” Toles said. “They already have PTSD from their home life so then they go to school and kids and sniff out their insecure nature so then we’re talking PTSD on top of PTSD on top of PTSD.”

Ages 8 to 11

As a child, serial killer Richard Ramirez, the “Night Stalker,” endured brutal beatings from his father. Ramirez, who began smoking marijuana and drinking alcohol by the age of 10, was introduced to the world of crime and drugs by his older cousin.

Ramirez’s cousin showed him photos of women he claimed to mutilate and murder while in Vietnam. His cousin, Michael Ramirez, later shot and killed his wife in front of Ramirez, who was 13 at the time. He told Ramirez not to tell anyone.

Ramirez went on a killing spree of his own in Los Angeles and San Francisco, which resulted in the murders of at least 14 people between April 1984 and August 1985. He was sentenced to death in 1989 and died while awaiting execution in 2013.

This goes on to suggest that the second influential life segment for serial killers takes place around the ages of eight and 11, Toles said.

Toles said sexual abuse for upcoming serial killers often take place around age eight. It can happen earlier, though.

Severe bullying could also be prevalent during this period. A person starts to develop within themselves, and when others abuse or bully the developing serial killer, the world altogether feels like it’s against them.

“It’s another huge event,” she said, adding that it typically is sexual abuse but can be severe bullying. “The whole world feels hostile.”

The issues during this time often make a person withdraw and become insecure, she said.

The split in the person’s psyche from ages three to five gets worse during the eight to 11 time period. A potential serial killer “acts like a compliant son or the compliant husband or the compliant neighbor.”

“There’s this whole other side of them,” Toles said.

The serial killer goes on to create “their own murder over and over again,” Toles said. The sex workers, in Heuermann’s case, represents how the serial killer feels about themselves: “discardable, not loved, not wanted.”

Hormones

The neurodevelopment of a person may play into a serial killer’s making, Toles said.

“You have a pressure cooker of all of these things happening and then the hormones happen and boom,” Toles said.

There are no known studies that have linked sexually motivated serial killers to having higher testosterone levels, which is often linked to aggression. Studies have found that an enzyme linked to serotonin and dopamine, called monoamine oxidase A, can be linked to violence. Men with low monoamine oxidase A are more likely to be convicted of a violent crime.

Some researchers have called this an “urge” that serial killers cannot fight. During his childhood, serial killer Edmund Kemper is said to have harmed animals. He apparently even buried a cat alive. He later dug it up, decapitated it and put the animal’s head on a spike.

Between 1964 and 1973, Kemper killed 10 people, including his mother and grandparents. Most of his murders included necrophilia, decapitation and dismemberment.

Kemper requested the death penalty. He instead received eight concurrent life sentences and has been incarcerated in the California Medical Facility since 1973.

In a 1993 study of more than 60 serial murderers, psychological and physical abuse were pervasive characteristics in a serial killer’s childhood. The study did not name specific serial killers it analyzed, but discussed the different disorders serial murderers may have, including a damaged prefrontal cortex, which controls emotional impulses.

“All humans aren’t that different,” Toles said. “It’s just that some people get pushed because of circumstances and things over certain lines.”

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