Junaid Hussain was considered one of the militant group's top online recruiters. Pictured: Iraqi security forces hold an Islamic State group flag they pulled down at the University of Anbar July 26, 2015. Reuters

A British hacker working with the Islamic State group was killed by a United States airstrike this week in Syria, the Pentagon confirmed Friday to reporters. Junaid Hussain, 21, was the only person to die in an airstrike targeting him Monday, U.S. Central Command spokesman Col. Pat Ryder told the Hill.

Hussain was believed to be behind the CyberCaliphate, a hacking group linked to ISIS that took control of the Central Command's social media accounts in January. He repeatedly published American soldiers' pictures, full names and addresses on Twitter, encouraging people to locate and murder them, the Wall Street Journal reported.

"Junaid Hussain's death removes a key ISIL [ISIS] member involved in actively recruiting and inciting sympathizers in the West to carry out lone wolf attacks," Ryder told the Hill. "He was also responsible for releasing personally identifying information of approximately 1,300 U.S. military government employees and specifically sought to direct violence against U.S. service members and government employees."

Hussain joined ISIS in Syria in 2013, a year after he was arrested for hacking former British Prime Minister Tony Blair's address book and posting its contents online, International Business Times previously reported. He was considered one of the extremist group's top recruiters, at one point tweeting "you can sit at home and play call of duty or you can come here and respond to the real call of duty ... the choice is yours."

The hacker was accused of radicalizing and encouraging the two men who opened fire at a Garland, Texas, competition between cartoonists drawing the Prophet Muhammad, CNN reported. He also allegedly worked with a team of people to organize a thwarted attack on London's Armed Forces Day parade earlier this summer.

Hussain was married to Sally Jones, a British punk rock musician now living in Syria. Jones reportedly has denied Hussain's death.