SACRAMENTO, Calif. — A refugee from Iraq was arrested Wednesday in Northern California on a warrant alleging that he killed an Iraqi policeman while fighting for the Islamic State organization.

Omar Abdulsattar Ameen, 45, and other members of ISIS killed the officer after the town of Rawah, Iraq, fell to the Islamic State in June 2014, according to court documents.

He was arrested by the FBI Joint Terrorism Task Force at a Sacramento apartment building based on a warrant issued in May by an Iraqi federal court in Baghdad. U.S. officials plan to extradite him back to Iraq under a treaty with that nation, and he made his first appearance in federal court in Sacramento on Wednesday.

Ameen could face execution for the "organized killing by an armed group" according to Iraqi documents filed in U.S. federal court.

Prosecutors say Ameen entered the U.S. under a refugee program, eventually settling in Sacramento, and attempted to gain legal status in the United States. It wasn't immediately clear when Ameen came to the U.S.