A Massachusetts Air National Guard member was arrested Thursday in connection with the disclosure of highly classified military documents about the Ukraine war and other top national security issues, an alarming breach that has raised fresh questions about America’s ability to safeguard its most sensitive secrets. The guardsman, an IT specialist identified as 21-year-old Jack Teixeira, was taken into custody without incident after FBI officers converged on his Massachusetts home. Attorney General Merrick Garland said he is to be charged with removing or transmitting classified national defense information, a crime under the Espionage Act. Garland did not reveal a possible motive, but accounts of those in the online private chat group where the documents were disclosed have depicted Teixeira as motivated more by bravado than ideology. While Thursday’s arrest was a pivotal moment in an investigation into the highest-profile intelligence leak in years, the military and Justice Department were still scrutinizing how sensitive government secrets shared in a chat room ended up circulating around the world. The emergence of Teixeira as a primary suspect is bound to raise questions about how such a profound breach, one that the Pentagon termed a “very serious risk to national security,” could have been caused by such a young, low-ranking service member. “We entrust our members with a lot of responsibility at a very early age. Think about a young combat platoon sergeant, and the responsibility and trust that we put into those individuals to lead troops into combat,” said Brig. Gen. Patrick Ryder, a Pentagon spokesman. Teixeira was a “cyber transport systems specialist,” essentially an IT specialist responsible for military communications networks, including their cabling and hubs. In that role Teixeira would have had a higher level of security clearance because he would have also been tasked with responsibility for ensuring protection for the networks, a defense official told The Associated Press, speaking on the condition of anonymity to discuss sensitive matters. Hours after the arrest, Rep. Mike Turner, the Republican chairman of the House Intelligence Committee, issued a statement pledging to “examine why this happened, why it went unnoticed for weeks, and how to prevent future leaks.” Teixeira, who was wearing a T-shirt and shorts at the time heavily armed tactical agents took him into custody, is due to have his initial court appearance in Massachusetts on Friday. He could also face charges in a military court. It was not immediately clear if he had a lawyer who could speak on his behalf, and a phone message left at a number believed to belong to his mother was not returned. Garland said the investigation is ongoing, but did not say if other suspects were being pursued.