A senior Islamic State commander involved in the execution of U.S. hostage Peter Kassig was killed in an airstrike in southeastern Syria on Sunday, the U.S. military said.

Col. Sean Ryan, a U.S. military spokesman, identified the Islamic State commander as Abu al-Umarayn and said he was killed in “precision strikes” in a desert area known as Badiya.

The coalition had reason to suspect that Umarayn posed an “immediate threat” to coalition forces in the area, Ryan said in an emailed statement.

Umarayn was also “involved in the killing of American citizen and former U.S. Army Ranger Peter Kassig,” the statement said, and he was linked to or directly involved in executing several other prisoners.

Kassig, who changed his name to Abdul-Rahman Kassig after he converted to Islam while in Islamic State captivity, was executed at some point in November 2014, a year after he was taken hostage in Syria. His captors released a video showing his decapitated head beside his body but did not include scenes of the execution, unlike with the other hostages they killed.

Umarayn is the first Islamic State figure to be publicly identified as having been involved in Kassig’s execution. He is also the first identified as having been killed in an airstrike since the U.S.-led coalition targeted Mohammed Emwazi, who was known as “Jihadi John,” in November 2015.

Emwazi had been the ringleader of a group of four Islamic State fighters nicknamed “The Beatles” by their captives and was identified as the man who appeared in the video of the execution of American journalist James Foley in August 2014.

The U.S. military did not say how they knew Umarayn was involved in Kassig’s killing or what role he may have played. He was with several other Islamic State members when the strikes were carried out, Ryan said.

In 2006-07, Kassig served in Iraq as a medic with the U.S. Army Rangers. At the time of his capture, he was volunteering as an aid worker in Syria, providing medical help and training to Syrians in areas hit hard by the country’s war. He was on his way to the province of Deir al-Zour in eastern Syria when he was kidnapped by the Islamic State, which is also known as ISIS, near the city of Raqqa.