WASHINGTON A U.S. Army sergeant who served in Iraq and Afghanistan and is now stationed in Hawaii has been arrested on charges of providing material support to Islamic State extremists, the Federal Bureau of Investigation said on Monday.

Ikaika Kang, 34, assigned to the 25th Combat Aviation Brigade, 25th Infantry Division, had been under investigation by the Army and FBI for more than a year and was taken into custody by FBI agents on Saturday, according to a bureau statement provided to Reuters.

According to a criminal complaint filed in U.S. District Court in Honolulu, Kang has sworn allegiance to Islamic State, also known as ISIS, the militant group that seized large swaths of territory in Syria and Iraq for a self-proclaimed caliphate.

He is also accused of attempting to provide military documents and training to the group, the FBI said in its statement.

Federal authorities believe that Kang, who was assigned to the Army’s Schofield Barracks on the island of Oahu, was a “lone actor” who had no known associations with anyone who might pose a threat to Hawaii, the FBI said.

He was slated to make an initial court appearance on Monday afternoon.

Kang, an air traffic control specialist who attained the rank of sergeant first class, served three overseas tours of duty – one each in South Korea (2002-03), Iraq (2010-11) and Afghanistan (2013-14), according to his Army service record.

The Schofield Barracks, about 17 miles (27 km) from Honolulu, was established in 1908 as a garrison for the Army’s defense of Pearl Harbor and the island of Oahu, and is home to more than 22,000 military personnel and family members.

The Army has sought to prevent a repeat of Islamist militant violence by one of its own since the 2009 shooting rampage at Fort Hood in Texas by then-Army Major Nidal Hasan, a U.S.-born Muslim who killed 13 people and wounded 32 others in an attack he claimed as retribution for American wars in the Muslim world.

(Additional reporting and writing by Steve Gorman in Los Angeles; Editing by Sandra Maler and Peter Cooney)