PHOENIX - The man suspected in the deadly Tucson shooting that killed six people and wounded U.S. Rep. Gabrielle Giffords was indicted Wednesday by a federal grand jury on three charges.

Jared Lee Loughner was indicted on one count of attempted assassination of a member of Congress and two counts of attempted murder of a federal employee (Giffords aides Ron Barber and Pam Simon), according to a U.S. Attorney's Office news release.

U.S. Attorney Dennis K. Burke said in the news release the investigation is in its early stages and could include potential death-penalty charges.

A conviction for the attempted assassination of a member of Congress carries a maximum penalty of life in prison, a $250,000 fine or both.

A conviction for attempted murder of a federal employee has a penalty of 20 years, a $250,000 fine or both.

Meanwhile, a preliminary hearing scheduled for Monday for Loughner, 22, has been moved to a larger federal courtroom in Phoenix. The courtroom is the centerpiece of the downtown Phoenix courthouse and is used mostly for ceremonial and high-profile hearings.

Thirteen people were wounded in the Jan. 8 attack at a grocery store.

Loughner is also facing federal charges in the deaths of U.S. District Judge John Roll and Gabe Zimmerman, an aide to Giffords. These indictments did not cover those cases.

State charges are pending.