ALEXANDRIA, Va. — Prosecutors brought the first-ever federal terrorism charges against a law enforcement officer in the U.S., alleging Aug. 3 that a patrol officer with the D.C. region’s Metro Transit Police was caught in sting buying about $250 worth of gift cards for the Islamic State group.

Nicholas Young, 36, of Fairfax, was arrested at Metro’s headquarters in Washington and charged with a single count of attempting to provide material support to a terrorist group. His initial court appearance is set for Aug. 3.

According to an FBI affidavit , Young bought the gift cards last month that he intended for the Islamic State to use to purchase mobile messaging apps, but Young actually gave the codes for the gift cards to an undercover FBI officer.

Young had been under surveillance since 2010, and he traveled to Libya twice in 2011, where he said he joined rebel forces seeking to oust dictator Moammar Gadhafi.

On one trip, he traveled with body armor, a Kevlar helmet and other military-style items, the affidavit said.

Young was deeply paranoid about law enforcement spying on him, often taking out the battery of his cellphone when he wanted to go somewhere and talk, the document said.

On Jan. 24, 2011, an undercover officer said Young told the officer he once aimed an AK-47-style rifle out of a window at his residence, scanning for law enforcement he believed was watching him.

On another occasion, he grew angry that the FBI talked to his family and co-workers and said he wanted to find the FBI agent and kidnap and torture her.

The undercover officer said he “doubted that Young seriously intended to act upon those words,” according to the affidavit.

As police searched Young’s townhome in Fairfax, neighbor Dina Ahmad described Young as standoffish. He had occasional run-ins with the homeowners’ association over his cluttered front lawn, she said.

He often worked on his car at late hours, and the car was adorned with anti-Israel bumper stickers, she said.

“We knew something was weird about him,” Ahmad said. “You just kind of got that creepy vibe off of him.”

Joshua Stueve, spokesman for the U.S. Attorney for the Eastern District of Virginia, said Young posed no threat to the Metro system, and nowhere in the affidavit does it mention the subway and bus system for the nation’s capital.

Metro spokesman Dan Stessel said Young, who had been employed since 2003, has been fired.

“Obviously, the allegations in this case are profoundly disturbing. They’re disturbing to me, and they’re disturbing to everyone who wears the uniform,” Metro General Manager Paul Weidefeld said in a statement.

FBI spokesman Andrew Ames confirmed that Young is the first law enforcement officer to be charged under the federal government’s terrorism law.

In 2014, Young met about 20 times with an FBI informant, and Young gave the source advice on how to avoid detection as he purportedly planned to travel overseas to join the Islamic State. Young frequently advised the source to watch out for informants.

Young was an associate of two other people charged with terror-related crimes. In 2010, law enforcement interviewed Young because of his links to Zachary Chesser, who eventually pleaded guilty to trying to join the militant group al-Shabab and to issuing threats to the makers of the South Park cartoon series after they penned an episode he found insulting to Islam.

Young also met regularly with Amine El Khalifi, who pleaded guilty in a sting operation in which he planned to attempt a suicide bombing at the U.S. Capitol in 2012.

During one conversation with an undercover officer, Young said if he was ever betrayed by someone, “that person’s head would be in a cinder block at the bottom of” a lake.

In March 2015, he raised suspicion when he brought a large amount of ammunition, AK-47s and a pistol to an off-duty weapons training event provided by another Metro officer. Young said he owned even more weapons, according to the affidavit.

He praised the 2015 Paris terrorist attacks at the Bataclan music hall and elsewhere, as well as the earlier Charlie Hebdo attacks, the document said.

While Young’s arrest is a first for a U.S. law enforcement officer, he is one of more than a half-dozen individuals from northern Virginia alone who have been charged with terror-related crimes, mostly in government sting operations. The FBI says it has ongoing investigations in all 50 states.

(MATTHEW BARAKAT)