A search warrant and other documents in the case of Hosam Maher Smadi, 19, show the items were seized from his residence in rural Milford, about 50 miles southwest of Dallas.
The documents show agents found a handgun, two loaded magazines and a box of 9mm ammunition. They also took a laptop, a digital camera and documents from the home.
Smadi was arrested Sept. 24 and faces a charge of attempting to use a weapon of mass destruction.
Authorities say Smadi parked a truck he thought contained a bomb in the garage beneath the 60-story Fountain Place office building in Dallas. Later, authorities say, he dialed a cell phone that he thought would ignite a blast.
Smadi's Brother Chooses Deportation
Meanwhile, Smadi's 18-year-old brother has told an immigration judge that he wants to go home to Jordan.
Hussein Smadi appeared before a San Francisco immigration court on Tuesday. He told the judge he wanted to rejoin his father in Jordan and offered to pay his own ticket.
Hussein Smadi entered the United States legally on a tourist visa in 2007, but stayed after it expired.
He was arrested on a drug charge and pleaded not guilty last month.
Through an attorney, Hussein Smadi said he had nothing to do with his brother, or any of the charges levied against him.