Alexander Hillel Treisman was first arrested in May after employees at a bank in Kannapolis, North Carolina, reported his abandoned white van in the parking lot, which led to the discovery by the police of several weapons and contraband inside, according to a court filing by the U.S. Court for the Middle District of North Carolina.
Officers observed weapons including an AR-15 style rifle, a canister of explosive material, and other ammunition boxes, federal prosecutors said. They also found more than $500,000 as well as several more firearms and "drawings of swastikas and planes crashing into buildings," according to the court filing.
Treisman was arrested soon after and the police and FBI initiated an investigation that uncovered that Treisman had a major interest in terrorist attacks and mass shootings, and had traveled around the country purchasing weapons in various states, according to federal prosecutors.
On Treisman's devices, investigators found that in April he posted a meme with the caption, "should I kill joe biden?" followed by a timeline of internet searches in May where he sought information on Biden's home address, state gun laws, and night vision goggles, the court filing said.
Investigators also found that he had traveled to a Wendy's restaurant within four miles of Biden's home and "wrote a checklist note ending with 'execute,'" according to the filing.
Additionally, the FBI uncovered "a total of 1,248 videos and 6,721 images of child pornography content ... in addition to 637 videos and images of child pornography containing sadism and/or masochism content," the filing said.
The Daily Beast first reported the court filing Thursday afternoon.
Kannapolis police arrested Treisman on May 28, according to federal prosecutors. The filing said that a day after his arrest, there was a jailhouse call between Treisman and his mother, Kimberly Treisman, "in which she suggests that [he] should 'jump bail.'"
The filing states that Treisman has no previous criminal history and that his counsel told the FBI he was diagnosed with Asperger syndrome at age 12, though he denied any having any mental health conditions in his initial interview with law enforcement.
It's not immediately clear why Treisman has not yet been charged with additional federal crimes other than possession of child pornography.
ABC News has reached out to the U.S. Attorney's office in the Central District of North Carolina for comment. Treisman's attorney did not immediately return messages from ABC News requesting comment.