NEW YORK (CBSNewYork) – A Brooklyn man originally from Kazakhstan who became a sniper and weapons trainer for the Islamic State group has been charged with terrorism crimes.

Prosecutors charged 42-year-old Ruslan Maratovich Asainov, a U.S. citizen who had a residence in Bay Ridge, after he was captured by Syrian authorities.

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According to investigators, in December 2013 Asainov traveled to Istanbul, a common transit point to gain entry into Syria. After entering Syria, he joined the ISIS terrorist organization, became a sniper and rose to the rank of “emir” in charge of training other ISIS members in the use of weapons.

In March 2015, Asainov asked a confidential informant to send him approximately $2,800 so that he could purchase a scope for his rifle.

READ: Ruslan Maratovich Asainov Detention Memo

Authorities say he wrote back in reference to ISIS, “We are the worst terrorist organization in the world that has ever existed,” and said he wanted to die on the battlefield.

“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,” stated United States Attorney Donoghue. “Our counterterrorism prosecutors and law enforcement partners will continue working relentlessly to hold accountable those like the defendant who have supported ISIS’s violent agenda.”

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Asainov’s attorney spoke moments after he appeared in court today.

“The judge entered a permanent order of detention, and we now await action by a grand jury,” she said. “He was very respectful, very cooperative with me, I don’t know what else to say.”

In June, a Syrian man who first arrived in New York as a refugee was arrested on terror charges involving a bomb plot in Pennsylvania.

A criminal complaint alleged Mustafa Mousab Alowemer planned to bomb an unidentified church on Pittsburgh’s north side, and purchased materials he thought were necessary to build a bomb. He also allegedly provided plans and a map to an undercover FBI agent he thought was a fellow Islamic State supporter.

In April, a Bronx man was arrested in Montana after he allegedly spoke to federal informant about joining ISIS and plotting a terror attack.

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Fabjan Alameti, 21, was charged with possession of a firearm by an unlawful user of a controlled substance and making false statements involving international and domestic terrorism.