Muhaxheri, aka Abu Abdullah al Kosova, is of Kosovo Albanian extraction. His NATO training reportedly included a stint at the U.S. Army's largest base in the Balkans. He has been designated a global terror threat by the U.S. State Department, and was regarded as a serious threat to Kosovo and Albania after joining ISIS.
Muhaxheri is an energetic recruiter for the Islamic State and one of its most public figures, popping up in a number of propaganda videos, including one where he kills a helpless captive with a rocket. (WARNING: graphic video at the link.)
He is believed to be the mastermind behind a thwarted plot to attack the Israeli national soccer team, Serbian Orthodox churches, and other targets in a string of synchronized terror attacks across the Balkans in November. Nineteen people were ultimately arrested in connection with the plan, and the authorities seized "weapons, explosives, and extremist religious materials."