A Co Down man at the centre of a global web of catfishing, blackmail and sexual abuse is believed by police to have targeted about 3,500 children.
From the bedroom of his childhood home near Newry, Alexander McCartney created a catfishing network which lured in victims across 30 countries.
The scale of the offending by McCartney stunned even the most experienced investigators, one describing it as a “paedophile enterprise”.
Between 2015 and 2019, the computer science student posed as a young girl on Snapchat or other forums. He would befriend girls between the ages of 10 and 16 who he would then persuade to send him topless photographs. Once he had the image, he would use it to blackmail the victims into performing sex acts.
Tragically, his offending led to the death of a 12-year-old girl in the US, Cimarron Thomas, who took her own life in May 2018 while in direct contact with McCartney, who was attempting to blackmail her into making her younger sister commit sex acts via a webcam.
McCartney, 26, has now been sentenced at Belfast Crown Court after admitting 185 offences relating to 70 child victims, which included manslaughter, blackmail, causing children to engage in sexual acts and making and distributing images of children.
McCartney first became known to police in 2016 when he was arrested in relation to indecent images of children found on his electronic devices. At this stage, no victims had been identified and he was bailed. He was arrested again on similar offences in 2018.
Despite the attention of police and bail conditions, McCartney continued to offend. He replaced phones and laptops which had been seized.
A prosecuting barrister told a pre-sentence hearing: “As time went on there was an escalation in the seriousness of his conduct in the form of the depravity of the demands he made of the subject children.”
In March 2019, Police Scotland contacted the Police Service of Northern Ireland (PSNI) in relation to a report of a 13-year-old girl who was being groomed by an adult suspect believed to be residing in Ireland. McCartney had posed as a young girl to “catfish” the victim.
When police raided his home, he was in the middle of offending and Snapchat was open on one of his phones. Devices seized from his bedroom were found to contain hundreds of thousands of indecent photographs and videos of underage girls.
Detectives soon realised that McCartney’s offending had spread around the world. Working with colleagues in the US Homeland Security and the UK's National Crime Agency, victims were located in the US, Australia, New Zealand and at least 28 other countries.
One source with knowledge of the investigation said his offending was “quite frankly, relentless”.
He began offending as a teenager, using multiple devices and operating across different time zones. The source said he built a “paedophile enterprise”.
While many of the victims have never been traced, based on the images recovered from his electronic devices, they are believed to number about 3,500.
The source said: “He has caused serious and long-lasting harm to multiple victims.”
His victims always believed, at first, that they were talking online to a girl of a similar age. McCartney used images of previous victims to create new profiles, assuming their identities as he targeted new children.
He targeted young girls who were vulnerable or professing doubts about their sexual identity and body image. He would use this vulnerability to persuade them to send a photo.
Once he had the image, McCartney would go to the notes section of his phone where he had a pre-prepared statement which he would cut and paste into the conversation.
The message would typically say: “alright i used a fake camera snap app. i have your face pic and nudes. You are gonna do as i say for tonight and then ill leave after. But if you dont them im upoading everything online for everyone to see. understand?”
Although McCartney promised to leave the victims alone after one night, he often returned later to continue the abuse.
He would blackmail them into sending more images or engaging in sexual activity online, threatening to share the images with other paedophiles. He forced some children into abusing younger siblings or forced them to involve family pets and objects.
The source said: “His depravity knew no bounds, he was abusing on an industrial scale.”
On one occasion, it took McCartney only nine minutes from meeting a 12-year-old girl for the first time until he had groomed, blackmailed and abused her.
The source said: “He became so proficient doing this, it took minutes for him contacting someone to getting pictures.”
In several of the videos seized by police, victims are seen pleading with McCartney to stop. One little girl repeatedly said she would kill herself and her mum was dying from cancer. He replied: “I do not give a shit about you or your mum.”
He told one victim who objected to his demands that he would get people to come to her house and rape her. Another who threatened to go to police was told: “I am secure, I have been doing this over a year.”
Crown Court judge Mr Justice O’Hara said transcripts of McCartney’s conversations with victims made for “excruciating reading”.
McCartney’s offending did not stop until he was remanded in custody in 2019. He was on remand in Maghaberry Prison until his sentencing.
In the early days of the investigation, much effort went into trying to identify the thousands of unknown victims whose images were on McCartney’s devices. When he appeared in court to face sample charges, prosecutors had to use the online ciphers of multiple victims who had not been traced.
In January 2021, McCartney was expected to plead guilty to close to 200 offences following one of the largest catfishing investigations anywhere in the world and one of the biggest criminal indictments in Northern Ireland’s legal history.
But the day before his court appearance, the PSNI was made aware that Cimarron, from West Virgina, had taken her own life in May 2018 after being blackmailed.
Detectives then travelled to the US to build a manslaughter case. As they investigated, they realised that McCartney was on an online call with Cimarron as she took her own life.
Detectives discovered McCartney had abused the girl some days earlier. She then returned to school believing her ordeal was over. But McCartney contacted her again, demanding she include her sister in the abuse.
During McCartney’s conversation with Cimarron, she pleaded with him to stop, telling him she would phone the police and take her own life.
He said he “did not care” and gave her a countdown before he threatened to send images of her to the first person on her contact list, her father.
Cimarron’s little sister found her body slumped in her parents’ bedroom. She died that night in hospital. Eighteen months later, Cimarron’s heartbroken father, Ben Thomas, also took his own life.
At one point, US authorities wanted to extradite McCartney, but this was not possible because he was already facing charges relating to the same crimes in Northern Ireland.
As part of building a manslaughter case against McCartney, prosecutors had to prove that he knew what he was doing would cause real, physical harm to victims. A number had been captured on video self-harming and several were traced and gave statements about their ordeals.
Between 2021 and March 2024, McCartney pleaded guilty to a series of charges. This included manslaughter relating to the death of Cimarron, the first such case in the UK where the victim resided in a foreign jurisdiction and had never met her killer in person.
The source said: “These children were in their own houses, their own bedrooms, their place of safety.
“Often being abused with parents in the house. It was unimaginable, your worst nightmare.”
Detective Chief Superintendent Eamonn Corrigan, of PSNI, said: “As far as I am concerned there is only one place for him and that is behind bars.
“Let this serve as a warning to those operating online and hiding behind fake accounts and firewalls, you will be caught and you will face the full force of the law when you are.”
