A prolific and deviant catfish abuser who drove a terrified 12-year-old girl to take her own life and left hundreds of others degraded and humiliated was jailed for life with a minimum of 20 years today.Alexander McCartney, a 26-year-old computer science student, caused Cimarron Thomas to use her father’s handgun to shoot herself in the head rather than submit to his perverted demands.Her US army veteran father Ben later took his own life after being consumed with guilt for leaving his gun where his ‘angelic’ daughter could access it.McCartney, of Newry, South Armagh, had pleaded guilty to the manslaughter of Cimarron at her home in Bruceton Mills, West Virginia, at a hearing earlier this year.He also admitted 184 other offences of blackmail and inciting a child to engage in sexual activity. A new photograph of Cimarron Thomas, 12, of Bruceton Mills, West Virginia, which was issued today following the sentencing of Alexander McCartney who drove her to take her own life A mugshot of Alexander McCartney who admitted manslaughter relating to Cimarron’s deathDelivering sentence at Belfast Crown Court today, Mr Justice O’Hara said McCartney had caused harm to young girls across the world.He said: ‘The prosecution has described the harm caused by the defendant as unquantifiable. I accept that description, subject to the proviso that the harm is inevitably and indisputably huge.’There were young girls, with younger siblings, all over the world, whose childhoods have been scarred by this defendant. In many cases that fact may not be known to their adult carers.’ Mr Justice O’Hara also told the court that the five years McCartney had already spent in custody would serve as part of his sentence. Cimarron’s grandparents, Peggy and Dale Thomas, spoke of their heartbreak in a victim impact statement read out in court. They said: ‘Our lives will never be the same again. We didn’t get to see her graduate, walk down the aisle or have children. We have been robbed and our lives have been changed forever.’The family also warned parents to remain vigilant against ‘evil’ communication online.They added: ‘We all have been devastated by our Granddaughter’s passing. We know that nothing that we do or say will bring her back. But if we can help another family to not have to go through what we did, something good could come out of her death. Parents, please keep the doors of communication open concerning the evil of some people online.’ In horrific messages between Alexander McCartney and one of his child victims, his perverted tactics are laid bare as he can be seen joking and flirting before suddenly turning nasty  Cimarron Thomas (left) with her US army veteran father Ben Thomas, who later took his own life after being consumed with guilt for leaving his gun where his daughter could access itThe former University of Ulster student had pretended to be a teenage girl when contacting hundreds of other young girls, many who were gay or unsure of their sexuality. Using the Snapchat and other social media he persuaded them to send topless photos – before revealing they had been catfished.Catfishing involves the use of a false identity online to befriend and exploit victims.He had first made contact with Cimarron Thomas in May 2018. After receiving intimate photos he tried to blackmail her into carrying out his deviant demands.Despite tearfully pleading with him to stop McCartney threatened to send the photos to her father and friends.When she refused his demands and said she would shoot herself he cruelly began a countdown and told her ‘goodbye and good luck’. Alexander McCartney (pictured), 26, operated from the bedroom of his family home in rural Northern Ireland and persuaded young girls to send naked pictures of themselves Cimarron and Ben Thomas with mother Stephanie. The double tragedy ripped apart the family Cimarron Thomas (pictured) was subject to sick blackmailing online by McCartney and used her father’s handgun to take her own life The youngster was found dying by her nine-year-old sister.Police who carried out the investigation into McCartney today released the emergency call made by a neighbour who has rushed to help the young girl.Much of the call is muffled, but the 911 operator can be heard telling the neighbour to apply pressure to the head wound.Cimarron’s 40-year-old father Ben took his own life 18 months after her death.At the time the family from a rural town had no idea why Cimarron had committed suicide.It was only in 2021 when police found a transcript of the conversation between Cimarron and McCartney they were able to tell them the reason for her death.He had kept the online chat as a ‘trophy’ on his computer. Cimarron (pictured with her father Ben) was told that if she did not comply with McCartney’s requests, her photos would be sent to her father Cimarron’s mother Stephanie (pictured left) still struggles to deal with the loss of her husband and daughter six years after the double tragedy – she is pictured here with Cimarron  The Thomas family initially had no idea why their daughter (pictured) had taken her life and were unaware of the depravity she had been subjected toFamily members told MailOnline that evil McCartney ‘might as well pulled the trigger’ and were outraged that he was not charged with murder.They had hoped that he would be extradited to the US, but State Department authorities say that will not happen.Members of the Thomas family said the double tragedy had torn apart their family with Cimarron’s mother Stephanie suffering from PTSD and six years on unable to bring herself to talk about her daughter’s death.Prosecutor David McDowell spent 90 minutes describing how McCartney had ‘degraded and humiliated’ his victims and showed no mercy when they pleaded with him to stop.McCartney refused to listen to the gut wrenching details of his campaign of abuse, sitting in the dock with his head bowed and hands covering his ears.Most of his victims were aged from between 10 and 16 and lived in the UK, Europe, America, Australia and New Zealand. McCartney used his technical knowledge as a computer science student to carry out his crimes, said the prosecution Cimarron Thomas, 12, (pictured) used her father’s handgun to take her own life after being blackmailed online by McCartney A tribute to Cimarron Thomas, 12, (pictured in the frame centre) who took her own lifePretending to be a girl, McCartney found and befriended girls who were said to be struggling with sexuality.He flattered them to get a compromising photograph and then used it to blackmail and threaten the teens into committing appalling acts.Each victim was left terrified that their intimate photos would be exposed to family and friends.McCartney told one girl that he would get people to come to her house to rape her if she didn’t comply.When another said her mother was dying of cancer he said ‘I don’t care’ and continued with his relentless abuse.Prosecutors said he carried out the abuse for his own sexual gratification.It only came to an end after a girl in Scotland complained that she was a victim of catfishing and the UK’s biggest catfishing investigation was launched.In March 2019 police in Scotland contacted their counterparts in Northern Ireland about a 13-year-old girl who had been groomed by an adult using the alias of someone her age.McCartney was traced and arrested. Pollice seized 64 devices and found tens of thousands of images of underage girls performing sex acts while being blackmailed.His lawyers said McCartney had showed genuine remorse and has been held on remand for five years since being arrested in 2019.