Jared Lee Loughner, who killed six people and shot former Arizona lawmaker Gabrielle Giffords in a 2011 rampage, kept bomb-making components in a safe in his bedroom, the Los Angeles Times reported on Friday.
Federal Bureau of Investigation (FBI) files released to the newspaper showed that agents and sniffer dogs, who stormed Loughner's home just after his capture, found equipment including batteries, a circuit board, wires, and a numeric keyboard, the LA Times said.
The files, amassed as the FBI investigated Loughner and released this week at the LA Times' request under the Freedom of Information Act, also showed his love of guns, erratic behavior and an obsession with Giffords.
The information in the report could not be independently confirmed by Reuters. The FBI did not immediately respond to requests for comment.
"I have a new tattoo on my back: 2 9mm bullets," Loughner wrote in one Internet message. "There are important figures in my dreams ... Hitler, (Hillary) Clinton and Giffords to name a few," he wrote, according to the files.
The former U.S. lawmaker was shot in the head on Jan. 8, 2011 during a "Congress on Your Corner" event at a Tucson supermarket, an attack that killed a U.S. judge and a 9-year-old girl and has added to a simmering national debate over gun laws.
Loughner, a college dropout with a history of mental illness, pleaded guilty and was sentenced to life in prison.
"If words could not be understood, then what does government mean?" then-student Loughner asked Giffords when she made an appearance at his high school, a former friend told investigators, the files said.
The students fell silent and had the feeling Loughner "went off the deep end", according to the documents, which also said Loughner was amazed at the inadequacy of Giffords' response.
The FBI files show Loughner had a 12-gauge shotgun, a 6-inch knife, a tan holster, and bullets, and had bragged to a longtime friend about a new Glock pistol he had bought.
The files suggest an obsession with Giffords, the newspaper said. A witness recalled Loughner at a library talking loudly "to the computer causing a disturbance to others in the area" and in one instance saw him viewing "Giffords' speeches online".
(Reporting by Eric M. Johnson; Editing by Louise Ireland)