The man accused of leaking hundreds of classified military documents had been doing so for months before getting arrested on Thursday.

Massachusetts Air National Guardsman 1st airman Jack Douglas Teixeira, 21, first began leaking paragraphs of text copied from classified documents back in December, according to the arresting affidavit. About a month later, he began taking photos of classified documents instead.

FBI ARRESTS JACK TEIXEIRA, AIR NATIONAL GUARDSMAN LINKED TO PENTAGON CLASSIFIED DOCUMENTS LEAK

Teixeira was allegedly releasing the information in essentially a chatroom on the Discord platform in a group of about 20-30 young men who share similar interests. His leaks were only uncovered weeks after another person within the group posted the classified information on another social media platform, where it then spread.

He had his first court appearance on Friday, where he was charged with unauthorized retention and transmission of national defense information and unauthorized removal and retention of classified documents or material, according to court documents. The judge scheduled a detention hearing for next Wednesday, and he will remain detained until then. Teixeira did not enter a formal plea.

The affidavit cited one member of the group who told law enforcement that the person who had been sharing the information called himself “Jack,” appeared to reside in Massachusetts, and claimed that he was in the United States Air National Guard. Law enforcement officials were then able to confirm Teixeira was behind the account after obtaining billing records from the platform. The unnamed individual referenced in the affidavit also identified Teixeira's driver’s license photo as the person he knew as “Jack.”

Teixeira is an enlisted airman with the Massachusetts Air National Guard at Otis Air National Guard Base, and he joined the service in September 2019. He's a cyber transport systems journeyman and has received one achievement medal during his time in the service, according to an Air Force spokeswoman.

He had a top-secret security clearance since 2021, and he maintained sensitive compartmented access (SCI) to other classified programs, so the documents he posted were accessible to him through his position.

Secretary of Defense Lloyd Austin was first briefed on the leaks on April 6, which is the same day Teixeira used his government computer to search classified intel reports for the word “leak,” presumably to see whether he was suspected of leaking documents, the affidavit alleged citing an unnamed government agency that can monitor certain searches conducted on its networks.

Teixeira allegedly shared hundreds of classified documents over the last couple of months, though many are still being uncovered on various social media platforms. The secrets contained within the documents give away U.S. intelligence sources, methods, and conclusions unintended for public knowledge that have the administration and Pentagon in damage control mode with allies.

Many of the documents pertained to the war in Ukraine, in which the U.S. is heavily invested. Some of them include U.S. intelligence on the Russian side, specifically regarding apparent fissures within Russian President Vladimir Putin's circle, as well as bleak assessments for the Ukraine spring offensive that officials have been expressing optimism for in recent weeks.

Other documents, some of which have been refuted by the countries involved, provided insights into the U.S.'s intelligence gathering on allies, including Israel, Egypt, and South Korea. Some countries have said the intelligence released about them was inaccurate or possibly disinformation.

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While at least one leaked document about the war in Ukraine appears to have been changed to Russia's benefit, it's unclear who would've manipulated them if not Teixeira.

The Pentagon is still reviewing how exactly this leak occurred and whether changes need to be made. The secretary directed Ronald Moultrie, undersecretary of defense for intelligence and security, to lead the review process on Thursday. He said he “will also not hesitate to take any additional measures necessary to safeguard our nation’s secrets."