U.S. Army sergeant Ikaika Kang, 43, has been arrested on charges of providing material support to Islamic State extremists. He has been under investigation by the Army and FBI for more than a year. (Reuters)

A U.S. soldier in Hawaii has been arrested on charges he sought to provide training and classified military secrets to Islamic State, officials announced Monday.

FBI spokesman Arnold Laanui confirmed that FBI agents arrested Ikaika Kang Saturday night, and he appeared in federal court in Hawaii on Monday.

Kang, 34, was employed as an Army soldier at Schofield Barracks in Hawaii, Laanui said. He was a sergeant and worked as an air traffic controller, according to an FBI affidavit filed in the case. Kang was in custody and could not immediately be reached for comment.

Court papers say Kang was deployed to Iraq from March 2010 to February 2011, and to Afghanistan from July 2013 to April 2014. He is highly trained in combat techniques and back in 2013 was a mixed martial arts competitor.

The FBI affidavit charges that Kang tried to help Islamic State “by providing both classified military documents, and other sensitive but unclassified military documents, to people he believed would pass the documents to ISIS. Kang did so with the intention that the documents would assist ISIS, including with fighting and military tactics. Additionally, Kang contributed to the purchase of a drone with the intention that it would be provided to, and used by, ISIS during fighting.”

Officials say warning signs about Kang’s behavior had been evident for years.

“He was reprimanded on several occasions for threatening to hurt or kill other service members, and for arguing pro-ISIS views while at work and on-post,” according to the affidavit. “Due to these remarks and threats, Kang’s security clearance was revoked in 2012, but reinstated the following year after Kang complied with military requirements stemming from the investigation.”

In private talks with a confidential informant, Kang praised the Orlando Pulse nightclub shooting and Adolf Hitler, according to the affidavit.

According to the court papers, the FBI used a number of undercover agents to win Kang’s trust, after which he gave one of the undercovers a set of classified documents, in the hopes they could help Islamic State with their military tactics.

After he was arrested July 8, Kang allegedly made a series of admissions to FBI agents.

He “said that he wanted to help the Islamic State as early as late 2015, because he saw how ill-equipped they were for the fight,” the affidavit said. “Kang confessed that he wanted to provide the Islamic State with weapons training as early as late 2015.”

The active-duty soldier who lives in Waipahu was charged with providing material support to the Islamic State terror group, and authorities say he not only swore allegiance to the group, but also attempted to give the group military documents, and attempted to provide training to the terror group.

FBI officials described Kang as “a lone actor” and said he has not associated with others who might present a threat to Hawaii.

“FBI assets and Army investigative resources were continuously deployed to ensure the public’s safety during the course of this investigation and Kang’s eventual arrest,” said Paul Delacourt, special agent in charge of the FBI’s Honolulu division.