An online predator who drove an American girl and her father to take their own lives has been jailed for at least 20 years in Britain’s biggest ‘fishing’ case.

Warning: This article contains references to suicide and child sexual abuse, which readers may find disturbing.

Alexander McCartney, 26, previously admitted 185 chargesincluding killing a girl who took her own life.

Police called him a “dangerous, relentless and cruel pedophile” who “may have pulled the trigger himself” and said there were around 3,500 victims.

Devices seized from his bedroom contained hundreds of thousands of indecent photos and videos of underage girls.

Belfast Crown Court heard the victims were aged between 10 and 16 and were based in the UK, US, continental Europe, Australia and New Zealand.

McCartney, from South Armagh, Northern Ireland, used Snapchat and other sites to pose as someone else online, known as catfishing.

He pretended to be a young girl to get his victims to send images. He then blackmailed them into sending more explicit material.

Cimarron Thomas, 12, of West Virginia, she shot herself with her father’s gun instead of complying with his demands after giving him an online countdown.

But there were more tragic repercussions.

Unable to live with the loss, her father Ben Thomas, a former US Army veteran, committed suicide 18 months later.

Former IT student McCartney pleaded guilty to one count of manslaughter, 59 counts of blackmail and 70 counts of inciting a child to engage in sexual activity.

At his sentencing, the judge said his offending began when he was 14.

“Completely Without Remorse”

McCartney admitted dozens of charges related to making and distributing indecent images of children and appeared “completely uncaring”, barrister David McDowell KC said.

The prosecution said he deliberately targeted victims who were either gay or exploring their sexuality and “degraded and humiliated” them.

The judge called the details “gritty” and much of what he did is too graphic and disturbing to detail.

McCartney told a girl he would send people to rape her if she didn’t comply. In some cases, he required his victims to involve younger siblings or even family pets and belongings.

A girl said repeatedly that she was going to kill herself and that her mother was dying of cancer.

“I don’t care about you or your mother,” McCartney replied.

The girl shot herself after McCartney’s countdown

In May 2018, posing as ‘Sarah’, he texted Cimarron Thomas at her family’s farm in the small American village of Bruceton and convinced her to send a topless photo.

When McCartney revealed she wasn’t Sarah, he demanded more explicit pictures and threatened to send them to her father.

When she asked him to stop, he told her to “dry her eyes” and engage her nine-year-old sister in sexually explicit material via webcam.

Belfast Crown Court heard that a police officer who reviewed the footage said Cimarron was “completely upset and crying”.

The court also heard that McCartney “counted down” online from 20 to zero as he insisted on more pictures.

Cimarron refused and shot himself.

McCartney’s last cynical message read: “Goodbye and good luck.”

Dad could not forgive himself

Cimarron’s younger sister heard what she thought was a balloon but found her lying on the floor of her parents’ bedroom. She died in hospital later that night.

Her father, Ben, could not forgive himself for leaving his gun within reach and took his own life 18 months later.

A statement read in court from his wife Stephanie said he felt guilty about his daughter’s death and had “lost interest in life”.

Cimarron’s family could not understand why he killed himself until three years later, when police found the online chat on McCartney’s computer.

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In a statement, Cimarron’s grandparents said: “We are all devastated by the death of our granddaughter.

“We know that nothing we do or say will bring her back. But if we can help another family not have to go through what we did, something good might come out of her death.

“Parents, please keep the doors of communication open about the harm of some people online.”

Detective Chief Superintendent Eamonn Corrigan, of the PSNI, said McCartney’s sentence was a “warning to those who operate online and hide behind fake accounts and firewalls – you will be caught and face the full force of the law then when you will be”.

Anyone feeling emotionally disturbed or suicidal can call Samaritans for help on 116 123 or email [email protected] in the UK. In the US, call your local Samaritens branch or 1 (800) 273-TALK.