How the police caught the catfish killer

It was a call from a 13-year-old girl in Scotland in 2019 that ultimately led to the capture of the social media predator described as one of the most prolific perpetrators of child sexual abuse in the world.

Alexander McCartney from Northern Ireland posed as a teenager to befriend and then abuse and blackmail children around the world, often sharing the photos with other pedophiles.

Some of the children were as young as four years old. Some people never told anyone what they had been through until the police knocked on their door.

McCartney gradually pleaded guilty to 185 charges, including murder after a 12-year-old girl he molested took her own life.

He will spend at least 20 years in prison.

Following contact with Police Scotland, an urgent investigation was launched in March 2019 by the Police Service of Northern Ireland (PSNI).

Detectives located Alexander McCartney’s home address, arrested him and questioned him.

Sixty-four of McCartney’s devices were seized from his home in the rural Lissummon Road area near Newry in four separate raids.

These devices contained hundreds of thousands of indecent images and videos of underage girls engaging in sexual acts while being blackmailed.

McCartney created and used multiple fake accounts on online platforms, mainly Snapchat, in order to entrap and manipulate them.

PSNI Det Ch Supt Eamonn Corrigan said McCartney had “committed crime on an industrial scale”.

He made the victims believe they were chatting online with a girl of a similar age and then encouraged them to send indecent photos or engage in sexual activity via webcam or mobile phone.

The detective said McCartney used the same pattern each time, adding: “He threatened to share these images online for the enjoyment of other pedophiles and use them to further molest and harass already terrified and abused children.”

In one case, it took McCartney just nine minutes to groom, sexually abuse and blackmail a girl as young as 12.

Over time, it became clear that McCartney’s depravity extended not only to Britain but to the entire world. Harassment included involvement with other people, pets and objects.

The PSNI worked with colleagues from the US Department of Homeland Security, the US Attorney’s Office and the National Crime Stoppers, with victims located in America, New Zealand and at least 28 other countries.

Many of these children were only identified through evidence found on McCartney’s devices.

According to the police, he “built a pedophile enterprise” and “stole the childhood” of his victims.

In the spring of 2019, the police summoned Catherine Kierans, acting head of the prosecutor’s office’s serious crimes unit.

They said “something big was happening… it involved catfishing.”

Catfishing is when a person creates a false identity to gain people’s trust and take advantage of it.

Ms Kierans stated that little girls aged 10-12 “were threatened in the most depraved way”.

She said some of the children who were abused had already spoken openly about their abuse, while others remained silent.

“Some children raised an alarm, which helped the police identify him.

“But some children never told anyone what they had been through until the police knocked on the door.”

According to Ms Kierans, McCartney was insulting “around the clock”.

As the investigation spread around the world, Kierans said prosecutors realized that McCartney was “trying very diligently to preserve the photos.”

“In some cases, he also saved a map of the child’s whereabouts on Snapchat, which then enabled police to locate the children.”

His 2021 arraignment was delayed after police discovered the suicide of a little girl in West Virginia, US.

“From the beginning, the level of violence was so horrific that we feared that once these children were identified, would anything happen to them?” – said Mrs. Kierans.

“Sadly, our worst fears were confirmed when we somehow learned that one of the little girls had taken her own life.

“Working closely with US authorities, we were able to prove that this child took his own life while being abused while continuing to interact with McCartney online.

“At that point, the child’s death was so inextricably linked to the abuse that we felt we had a strong case to say he killed her.”

That little girl was 12-year-old Cimarron Thomas, who shot herself in 2018 after McCartney molested her.

McCartney was charged with manslaughter.

Kierans said it is believed to be the first case in the world in which an abuser was held accountable for a murder in which the victim and perpetrator never met in person.

The case was so serious that prosecutors had to be judicious in bringing charges.

“We couldn’t put 3,000 counts in the indictment,” Kierans said.

“Ultimately around 200 charges were laid (involving approximately 70 victims), which is probably one of the largest indictments we have seen in Northern Ireland.”

McCartney grew up five miles from Newry, just off the main road into Armagh.

It’s as rural as it gets. Farms, a church and several businesses.

When he first appeared at Newry Magistrates’ Court in July 2019, he was just 21, with long, curly hair and the wide-eyed look of someone surprised to be sitting where he was.

He spent more than five years in custody at Maghaberry Prison, only being released for court hearings and further police interviews.

During these interrogations, he said little other than confirming his name and date of birth and making a gradual, silent admission of guilt.

McCartney attended Newry High School and was interested in games.

One source told BBC News NI: “He was introverted and socially awkward. He didn’t interact much with people outside his group of friends.

“He may have been on the receiving end of things, but he had friends who didn’t seem to know anything about it.”

He then took a course at Southern Regional College, Newry, where he was described as “quiet and not very involved in the rest of the classes”.

When charges were finally brought against him in 2019, he was a computer science student at the University of Ulster.

The case was shocking for the residents of his house and the surrounding area.

“The whole place was stunned,” one resident said.

“At first it was whispers, then disbelief. I’m sure people talk about it in their homes, but it’s not discussed publicly because people don’t know what to say.

Another said: “He seemed like a nice, likeable and intelligent young man.

“There’s nothing extraordinary about it.”

But what is extraordinary is the horror of his crime; many of his victims pleaded for an end to the violence, but prosecutors said he “callously continued, at times forcing victims to engage younger children, some as young as four years old.”

According to Catherine Kierans, McCartney’s depravity was so great that it was “one of the most disturbing and prolific cases of child sexual abuse we have ever seen in the PPS”.

Kierans said that despite exhaustive efforts, police still failed to identify some of the victims.

“McCartney’s crimes harmed thousands of children and left them and their families facing traumatic consequences,” she said.

“Their courage contrasts sharply with his cowardice in attacking defenseless young girls.”

Further information and support for those affected by this story can be found on the website BBC Action Line.