Washington, Reuters/Asharq Al-Awsat—A British hacker who US and European officials said became a top cyber expert for Islamic State of Iraq and Syria (ISIS) has been killed in a US drone strike, a US source familiar with the matter said on Wednesday.

It was the second reported killing of a senior ISIS figure in the last eight days. ISIS’s second-in-command was killed in a US air strike near Mosul, Iraq, on August 18.

The source indicated that the US Defense Department was likely involved in the drone strike that killed British hacker Junaid Hussain, a former resident of Birmingham, England.

A report on the website CSO Online said the drone strike took place on Tuesday near the Syrian city of Raqqa.

US and European government sources told Reuters earlier this year that they believed Hussain was the leader of CyberCaliphate, a hacking group which in January attacked a Twitter account belonging to the Pentagon, though the sources said they did not know if he was personally involved.

Hussain moved to Syria sometime in the last two years. He was 21 years old, the Birmingham Mail newspaper reported.

Hussain is believed to have led a group of other ISIS hackers from his base in Raqqa and overseen the production and distribution of numerous propaganda videos used by ISIS for intimidation and recruitment purposes.

US government sources said that in his role as ISIS’s cyber chief, Hussain recently had become a subject of considerable interest to US security and defense agencies.

However, the sources denied a recent British news report that said he was No. 3 on a US list of drone targets, saying other operational ISIS commanders were regarded by US authorities as far more dangerous than Hussain.

The killing of Hussain, if confirmed, “would represent a major blow to ISIS and other terrorist groups” operating out of Syria, experts said.

“The importance of the killing of influential ISIS elements, like Hussain, lies in the fact that they tend to operate off the radar, without seeking positions of authority or official titles while at the same time they commit the dirtiest of acts inside and outside Syria,” Luay Al-Miqdad, director of Masarat, a group that monitors terrorist activity in Syria, told Asharq Al-Awsat.

Miqdad called on the US-led anti-ISIS coalition “to conduct more operations of this type in order to deprive ISIS from feeling safe and the people of the ISIS-occupied Raqqa from feeling they have been left to face their fate alone.”

According to Miqdad, the Syrian people share “a common interest with the US-led coalition countries in dismantling ISIS and striking its leaders.”