PHOENIX -- The suspect in the attempted assassination of Rep. Gabrielle Giffords was hit with dozens of new charges as federal prosecutors formally accused him of killing six people and wounding 13 others during a Tucson shooting rampage.

Jared Lee Loughner was charged in a 49-count grand jury indictment last week stemming from a Jan. 8 shooting at a political event held by Giffords outside a grocery store.

"This indictment is comprehensive and is solid, and covers all the murdered and injured victims," federal prosecutor Dennis Burke said. "There are no distinctions at all between the victims. These victims were exercising one of the most precious and fundamental rights of American citizens."

Giffords is recovering from a gunshot wound to the head at a Houston hospital. In recent days, she has been talking and singing some of her favorite songs as part of her speech and musical therapy.

The indictment against Loughner charges him in the murders of U.S. District Judge John Roll and Giffords aide Gabe Zimmerman, and with causing the deaths of four others who were not federal employees, including a 9-year-old girl.

Loughner also was charged with causing the death of a participant at a federally provided activity; injuring a participant at a federally provided activity; and using a gun in a crime of violence.

Loughner had pleaded not guilty to earlier federal charges of trying to assassinate Giffords and kill two of her aides.

His attorney, Judy Clarke, didn't return a call and e-mail left at her office Friday.

Federal prosecutors haven't yet said whether they will seek the death penalty against Loughner. But legal experts believe it's a virtual certainty.

Loughner will likely face state charges in the attack as well, but will be tried first in federal court.

Loughner is expected to be arraigned on the new charges Wednesday in Tucson.