A man in Northern Ireland has been sentenced to life for several crimes, including manslaughter, after using social media sites to blackmail and sexually abuse at least 70 minors in several countries.

Alexander McCartney, 26, was sentenced by a judge at Belfast Crown Court on Friday for child sexual offenses, blackmail and the manslaughter of a 12-year-old girl who took her own life in the United States in 2018 after being “catfished,” according to a statement from Northern Ireland’s Public Prosecution Service (PPS).

Catfishing – often used on social media – is when a person uses false information and images to create a fake identity online with the intention of tricking, harassing, or scamming another person.

According to authorities, McCartney pretended to be a young girl, befriended victims on social media and manipulated them into sending him nude images of themselves.

The victims were then threatened “into sending him indecent images and videos of themselves, forcing them to engage in depraved and sometimes dangerous sexual acts,” the statement said.

McCartney – who targeted around 3,500 girls from Northern Ireland, Ireland, Great Britain, the US and New Zealand – sought to “exploit that vulnerability in the most shocking ways,” acting head of the PPS Serious Crime Unit Catherine Kierans said.

“All McCartney’s victims were young, innocent children” as young as 10 years old and “struggling with identity and body image issues and had reached out for help on social media,” Kierans said.

In total, McCartney pleaded guilty to 185 charges involving 70 victims. McCartney must serve a minimum of 20 years in prison before he can be considered for parole.

“Tragically, one of his young victims, who was just 12, had taken her own life during an online chat in which he was threatening her and forcing her to engage in sexual activity,” Kierans noted. She said that the girl, an American, and McCartney never met in person.

“If we discover this activity, or it is reported to us, we remove it, lock the violating account and report it to the authorities,” the social media site said. It added that the app has “extra protections for teens to make it difficult for them to be contacted by strangers.”

The PPS is working to identify more of McCartney’s victims, according to its statement.