A U.S. citizen has been arrested and charged for allegedly providing materials, including services, training, and personnel, to ISIS, federal prosecutors announced Friday. According to the criminal complaint, Ruslan Maratovich Asainov, 42, visited Syria in 2013, where he joined ISIS and become a sniper, eventually rising through the ranks to become in charge of training other ISIS members on how to use weapons. In March 2015, Asainov allegedly asked an informant to send him $2,800 to purchase a scope for his rifle. He messaged an associate to say that ISIS was “the worst terrorist organization in the world that has ever existed,” according to the complaint.

U.S. Attorney Richard Donoghue said that “the defendant, a naturalized U.S. citizen residing in Brooklyn, turned his back on the country that took him in and joined ISIS, serving its violent ends in Syria and attempting to recruit others to its cause,” adding that law enforcement will continue to chase down supporters of ISIS. Asainov was transferred into FBI custody Wednesday and will appear in court on Friday.