Jack Teixeira, the Massachusetts Air National Guard member charged with leaking classified U.S. intelligence documents on a gaming platform, alarmed fellow members of his unit, who worried that the young computer technician might, in the words of one, “shoot up the place” after he was warned to stop looking at classified information that had nothing to do with his job, according to documents obtained by The Washington Post.

Teixeira often discussed his love of firearms at work and said he wanted to acquire more weapons, including machine guns, suppressors and explosives, and talked about “living off the grid” or on a large piece of land so he could “blow stuff up,” according to an Air Force Inspector General report released through a Freedom of Information Act request filed by The Post.

Investigators who spoke to Teixeira’s colleagues at Otis Air National Guard Base on Cape Cod after his arrest on April 13 found that his disturbing comments prompted one airman to warn a commander that Teixeira, now 22, “exhibited a fringe thinking perspective” that seemed comparable to that of Ted Kaczynski, the domestic terrorist popularly known as the Unabomber, who killed three people and maimed others.

Colleagues were aware, the investigation found, that Teixeira had been suspended in high school for threatening to bring weapons to campus, language that prompted fellow students to report him to school officials and later to local police. Some of Teixeira’s fellow airmen referred to him as “the active shooter kid,” according to the Air Force report.

The Defense Department released an executive summary of the investigation earlier this month that documented widespread failures in Teixeira’s unit at the 102nd Intelligence Wing and cited a “culture of complacency” and “lack of supervision” that allowed him to read and ultimately remove huge amounts of classified information. The Air Force disciplined 15 members and relieved the wing commander.

Teixeira is alleged to have committed one of the largest national security breaches in decades, leaking hundreds of top-secret files detailing the war in Ukraine, U.S. surveillance of allies and enemies, and intelligence and analysis on hot spots across the world.

An Air Force spokeswoman, Ann Stefanek, said Friday that disciplinary actions were taken against personnel in the unit “because they did not take the actions necessary to report the threat nor safeguard classified defense information.” She noted that the unit still has not been cleared to resume its intelligence mission.

But the summary of the report did not include the detailed accounts of Teixeira’s concerned co-workers, who said that as early as the summer of 2021 he exhibited the warning signs they had been trained to look out for in a potential active shooter. The fuller report shows that Guard members who worked with Teixeira him saw him as a security risk, but not for the reasons that ultimately led to his arrest and indictment this year on charges of illegally removing and disseminating classified information.

Yet those two potential threats appeared connected, the investigation found.

One co-worker, whose name is redacted in the report, noted a “personality shift” in Teixeira, who was described as “demoralized and depressed” after he received a warning to stop reading classified information. As a computer technician, Teixeira’s job was to maintain the networks on which classified documents were stored, but not read the information.

Teixeira “seemed like a completely different person” after he was admonished, and the colleague was concerned that Teixeira “might do something drastic,” the investigation found.

That colleague told another of Teixeira’s co-workers to “keep an eye on” the young airman. That second person understood that his superior was “worried [Teixeira] would bring a gun to work that night,” the report said. It also noted that Teixeira had on occasion shown up for work late and failed to attend a scheduled training event. When a supervisor asked Teixeira to explain his absence, he “provided an unprofessional and crass response,” according to the report.

The investigation also found that Teixeira once left his car running for an extended period of time on base, arousing suspicion. A security officer noticed numerous used paper shooting targets and a large military-style backpack in the back seat. Teixeira offered to allow a search of the vehicle, but the officer declined, the investigation found. Authorities determined that Teixeira owned more than a dozen registered firearms.

For all the concerns about Teixeira’s suspicious behavior and potential for violence, no one in the unit reported him to the appropriate security officials, the investigation found. Instead, investigators documented a pattern of buck-passing and downplaying of worries that Teixeira, who one described as simply “a dumb Airman doing dumb things,” was really a danger. The concerns that Teixeira fit the profile of a potential active shooter were only reported to the appropriate Air Force investigators after he was arrested in connection with the document leaks, in April of this year.

Even that event, which was covered by news organizations around the world, failed to register with another member of the unit, who attempted to schedule Teixeira for duty two weeks after his arrest. That action, following “a monumental national news event occurring within the unit,” was a “stark example of [the member’s] lack of situational awareness or appreciation for the gravity of the matter,” the investigation found.

Among those previously punished by the Air Force were Col. Sean Riley, who was commander of the 102nd, and Col. Enrique Dovalo, the former commander of the subordinate 102nd Intelligence, Surveillance and Reconnaissance Group, to which Teixeira reported. Riley was relieved of command Nov. 1. The Air Force did not disclose the nature of Dovalo’s punishment.

Neither officer responded Friday to requests for comment. The Massachusetts Air National Guard also did not respond to requests for comment. Earlier this month, officials with the Guard said in an email that they would not grant interviews or make either officer available for comment.

The inspector general’s investigation did not offer a potential motive for Teixeira’s alleged leaks. A lengthy investigation by The Post and PBS’s “Frontline” found that Teixeira wanted to impress friends he met online in the gaming platform, Discord. Around the time of Russia’s invasion of Ukraine in February 2022, Teixeira began to post classified information about casualty figures, which led to more regular updates on the status of combat, friends said. He eventually shared hundreds of classified documents covering a huge range of topics, according to friends who read the material.

Friends described Teixeira as a conspiracy theorist who thought the government was hiding true information about the war and other security concerns from the public. They said Teixeira seemed to enjoy sharing access to secrets that weren’t available to regular people.

Teixeira said as much to a co-worker at the base, the Air Force investigation found. He was asked why he was so interested in a top-secret Defense Department network where he’d been looking at classified documents.

Teixeira replied, “I like knowing things other people don’t.”