The US-led coalition against the ISIS group said Monday it killed a senior terrorist involved in the executions of an American aid worker and other Western hostages. ISIS executioner Abu al Umarayn was killed on Sunday along with several other members of the terror group in a series of precision strikes. He was involved in the November 2014 beheading of Peter Kassig, a US aid worker and former Army Ranger who was captured in 2013. A video posted online showed British "Beatles" ISIS member "Jihadi John" - who was later killed in an airstrike - standing over Kassigs severed head. "He was killed and more information will be available after a full assessment," Sean Ryan, spokesman for the US-led coalition, said in a statement issued after the Sunday strikes. "Al Umarayn had given indications of posing an imminent threat to coalition forces and he was involved in the killing of American citizen and former US Army Ranger, Peter Kassig," he said. Ryan said the militant had also been involved in the execution of several other prisoners. It is the first time the coalition, which has been hunting down ISIS fighters in Iraq and Syria since 2014, has announced the killing of a radical leader linked to Kassigs death.