AL-BAB, SYRIA — The Islamic State lost one of its most senior officials in an American airstrike in Syria, in what most see as a crushing blow to the terrorist organization.

Reuters reports that the U.S. has confirmed that it targeted a vehicle carrying Islamic State spokesperson Abu Muhammad al-Adnani in the Syrian city of al-Bab. U.S. forces mounted an air strike on the vehicle as it was traveling in the city on Tuesday.

Adnani is believed to have been killed in the strike, though U.S. defense officials did not immediately confirm this. ISIS’s own news agency announced his death the same day, but said only that he was killed while checking out operations in Aleppo province.

According to the New York Times, Adnani was the group’s chief propagandist, and was responsible for recruitment and external operations. He organized attacks in countries including France, Belgium, and Turkey, and famously called for ISIS supporters to launch lone wolf attacks in Europe and the U.S.

Adnani was not the only high-ranking ISIS official lost this year. ‘Minister of War’ Abu Omar al-Shishani was killed under similar circumstances in July.