WASHINGTON (AP) — A top assassin for the Sinaloa drug cartel who was arrested by Mexican authorities last fall has been extradited to the U.S. to face drug, gun and witness retaliation charges, the Justice Department said Saturday.

Néstor Isidro Pérez Salas, also known as “El Nini,” is a leader and commander of a group that provided security for the sons of imprisoned drug lord Joaquín “El Chapo” Guzmán, and also helped in their drug business, federal investigators said. The sons lead a faction known as the little Chapos, or “Chapitos,” that has been identified as one of the main exporters of the deadly synthetic opioid fentanyl to the U.S.