In a filing late Wednesday, prosecutors said he had destroyed evidence in the case and they also pointed to his history of making violent threats online, saying he should be detained pending trial because he is a flight risk and poses a threat.
"The defendant undoubtedly poses a danger to the U.S. at large based on his ability to cause exceptionally grave danger to the U.S. national security," according to a motion filed by the office of U.S. Attorney Rachael Rollins.
"However, there is also evidence to suggest that the defendant may also pose a physical danger to the community."
Teixeira, who lived with his mother and stepfather, kept a gun locker two feet from his bed, which contained handguns, bolt-action rifles and a military-style rifle with a high-capacity magazine, according to the government's filing.
FBI agents also found a gas mask, ammunition and what appeared to be a "silencer-style accessory in his desk drawer," the government said.
Prosecutors say the 21-year-old leaked classified documents, including some relating to troop movements in the Russia-Ukraine conflict, to a group of gamers on the messaging app Discord.
In 2018, while in high school, Teixeira was suspended after he was overheard making racial threats and remarks about guns. Teixeira attributed those remarks to a reference in a video game, according to prosecutors.
More recently, in November 2022, Teixeira said if he had his way, he would “kill a ton of people” because it would be “culling the weak minded,” prosecutors alleged in documents supporting their motion to detain Teixeira.
His attorneys on Thursday sought to downplay the high school incident, saying it was "thoroughly investigated" and that he was allowed to return to school after a psychiatric evaluation.
"The investigation was fully known and vetted by the Air National Guard prior to enlisting and also when he obtained his top-secret security clearance," they added.
