In the weeks and days before the shooting rampage in Tucson, suspect Jared Lee Loughner surfed the Internet on his computer in what investigators believe was an effort to prepare for his alleged assassination attempt, law enforcement sources familiar with the investigation said.

Loughner pulled up several websites about lethal injections and solitary confinement in prison, said the sources, who asked to be anonymous because the investigation is ongoing. He also viewed Internet sites about political assassins, according to an analysis of Loughner's computer that was completed by investigators last week, the sources said.

Police seized Loughner's computer when they forcibly entered his family home in Tucson on Jan. 8, shortly after the shooting outside a Safeway that killed six people and injured 13 others, including Rep. Gabrielle Giffords. He has entered a not guilty plea in connection with federal charges.

On the night before the shooting, Loughner rented a room at a Motel 6 near the railroad tracks on the western edge of Tucson. Using the room as a staging ground for a series of pre-dawn errands, Loughner drove back and forth several times between the motel and his home, where he used his computer for the last time, sources said. At one point early in the morning, he posted a bulletin on his Myspace page titled "Goodbye friends," according to investigators.

Prosecutors hope to use the information found on Loughner's computer, along with notes seized in his home, to indicate that Loughner, 22, was not insane and knew right from wrong. They have turned over to the defense the information they obtained from the computer, as well as discs containing about 250 interviews conducted by investigators.

"The impression investigators have is that he was trying to educate himself on assassinations and also research the consequences," said one source close to the investigation. The source said Loughner pulled up sites that explained the process and effects of lethal injections.

Special Agent Jason Pack, a spokesman for the FBI, would not comment on the information in Loughner's computer, which is in the the FBI's possession. Jason Ogan, spokesman for the Pima County Sheriff's Department, also would not comment and said the sheriff would make no further comments on the investigation.

Loughner was arraigned in a federal courthouse in Phoenix on Monday. His hearing in the case is set for March 9.