TUCSON - A federal grand jury indicted accused Tucson gunman Jared Lee Loughner on three counts Wednesday, with prosecutors saying more indictments could be on the way for the 22-year-old.

The news came on the same day that aides to wounded Rep. Gabrielle Giffords (D-Ariz.) announced her transfer, scheduled for Friday, from a trauma center here to a rehabilitation hospital in Houston.

Loughner will be arraigned in a Phoenix courtroom Monday. U.S. Attorney Dennis K. Burke announced that he was charged with attempting to assassinate Giffords and with two counts of attempting to murder her congressional aides, Ron Barber and Pam Simon, in the Jan. 8 shooting rampage that killed six and wounded 13. Those charges carry maximum sentences of life in prison and 20 years, respectively.

Loughner also has been charged with killing District Judge John Roll and Giffords aide Gabe Zimmerman. If indicted in those killings, he would face the death penalty.

Justice Department rules "require us to pursue a deliberate and thorough process," Burke said in a statement. "Today's charges are just the beginning of our legal action. We are working diligently to ensure that our investigation is thorough and that justice is done for the victims and their families."

Loughner is likely to also face state murder charges in the deaths of the four others who were not federal employees.

Giffords remains in serious condition at Tucson's University Medical Center after being shot in the face at close range. Barring unforeseen complications, she will be transferred Friday to the TIRR Memorial Hermann rehabilitation hospital in Houston, her aides said.

"I am extremely hopeful at the signs of recovery that my wife has made since the shooting," said her husband, astronaut Mark Kelly, who has been at her bedside.

The family also considered Washington's Walter Reed Army Medical Center and facilities in New York and Chicago. But Kelly said the Houston hospital is near where he lives and where he trains, at NASA's Johnson Space Center.

The news of a hospital transfer was hailed by well-wishers in Tucson who have streamed to makeshift tributes outside the medical center and Giffords's local office, leaving cards, stuffed animals, signs and candles for the 40-year-old congresswoman.

To Jennifer Wright, 51, who was outside the office Wednesday wearing a T-shirt covered with peace signs, Giffords's departure from Arizona will be bittersweet because it could mean an extended absence from her community. "Knowing she's right here down the street has been comforting," Wright said.

Inside the office, the mood was lifted by the presence of dozens of stuffed animals that were collected from the memorial for donation to local children's charities.

Experts cautioned that Giffords still has a long road ahead. Michael Yochelson, director of the brain injury program at the National Rehabilitation Hospital in Washington, said she faces up to three months of in-patient care, followed by an additional two to four months of therapy after she is discharged.

Yochelson described an intense regimen for patients with brain injuries like Giffords's: physical therapy (for strength and coordination), occupational therapy (for basic skills such as grooming and dressing), speech therapy and neuropsychology (for cognitive functions and emotional support).

The risks include infection and pneumonia, as well as partial blindness.

"It is a long haul," Yochelson said.

TIRR Memorial Hermann is ranked as the nation's fifth-best rehabilitation center by U.S. News and World Report.

nakamurad@washpost.com sandhya@washpost.com

Staff writers Jerry Markon in Washington and Sari Horwitz in Las Vegas contributed to this report.