A prolific "catfish" offender whose cruel campaign of global online blackmail targeted thousands of young victims and drove a 12-year-old US girl to suicide was on Friday jailed for life.
Alexander McCartney, 26, posed online as a teenage girl to befriend young females across the world on the social media app Snapchat, forcing them to send him explicit pictures, then threatening to make them public.
He admitted 185 charges involving 70 children and was told he would spend at least 20 years behind bars.
Detective Chief Superintendent Eamonn Corrigan, of the Police Service of Northern Ireland, said McCartney was a "disgusting child predator" whose offending had been on an "industrial scale".
"Sitting in his childhood bedroom in Newry (in Northern Ireland), he began his offending as a late teenager and built what can only be described as a paedophile enterprise," he told reporters outside court.
"McCartney is a dangerous, relentless, cruel paedophile," he added.
Cimarron Thomas from West Virginia in the United States took her own life in May 2018 after McCartney demanded that she involve her younger sister in sex acts he had coerced her into.
Eighteen months later, her distraught father Ben Thomas also died by suicide.
Belfast Crown Court heard earlier other victims had been in the United States as well as in Australia and New Zealand.
Sentencing McCartney, judge John O'Hara said he was unaware of any other case in which an offender had used social media to "inflict such terrible and catastrophic damage on young girls up to and including the death of a 12-year-old girl".
"It is truly difficult to think of a sexual deviant who poses a greater risk than this defendant," he added.
O'Hara said McCartney had been "remorseless" in his offending, ignoring "multiple pleas for mercy".
Even after his third arrest, he said, the former computer science student kept offending in "an even more sinister, dramatic and appalling manner".
McCartney previously pleaded guilty to manslaughter relating to Cimarron's death.
Corrigan told reporters McCartney had even started a countdown when Cimarron threatened to kill herself with a legally owned firearm and told her: "I don't care."
"He may as well have pulled the trigger himself," he added. "There's only one place for him, that's behind bars."
McCartney also admitted 59 counts of blackmail, dozens of charges related to making and distributing indecent photographs and scores more of inciting children to engage in sexual activity.
Police in Northern Ireland worked with other forces internationally to bring him to justice.
Derek Gordon, the US special agent in charge of Homeland Security Investigations based in Washington DC, praised the investigation and prosecution of McCartney by Northern Irish counterparts as "nothing short of brilliant".
"Alexander McCartney committed some horrific and disturbing crimes and deserves every minute he serves in prison," he said.
Catherine Kierans, from the Northern Ireland Public Prosecution Service, said McCartney was estimated to have targeted 3,500 girls, some as young as 10.
Despite exhaustive efforts, however, many of his victims may never be identified.
She urged any child or young person to seek help if they were being threatened by someone demanding sexual images or videos.
"This is a crime. You are not to blame. Please talk to a trusted adult," she said, praising the bravery of the victims who had helped to convict McCartney.
And she called on parents and carers to talk to their children to keep them safe online.
"It is by bringing these issues out into the open that we can break the cycle of secrecy abusers rely on," she said.
