The U.S. federal prosecutors have filed five charges against the suspect in the multiple shootings in a grocery store in Tucson, Arizona, in one of the most deadliest shooting sprees in the U.S. history, the authorities said Sunday.

Candles are seen lighted up for those dead and injured people during a shooting outside the medical center of Arizona University in Tucson, Arizona, United States, Jan. 8, 2011. The alleged shooter intended to kill Congresswoman Gabrielle Giffords when he pulled the trigger of a pistol in a shooting spree which also claimed lives of five others including U.S.District Judge John Roll and wounded 12 others at a supermarket in northwest Tucson, Arizona Saturday morning, officials said. [Qi Heng/Xinhua]

Jared Lee Loughner, 22, is charged with attempted assassination on Congresswoman Gabrielle Giffords, two counts of killing an employee of the federal government and two counts of attempting to kill a federal employee.

The charges are preliminary, FBI Director Robert Muellers said earlier at a press conference. Additional charges could be brought under domestic terrorism statutes as the investigation continues, he added.

Loughner refused to talk to investigators, invoking his right to remain silent.

Giffords was shot in the head at her first public appearance with her constituents since she was re-elected to third term in the U.S. Congress near Safeway supermarket in Tucson. The attack, which apparently targeted the congresswoman, killed six people and wounded 13 others.

Among the dead were U.S. District Judge John Roll; Gabe Zimmerman, a 30-year-old aide to the congresswoman; Christina Taylor Green, a 9-year-old girl who had just been elected to her school's student council. Also killed were Dorthy Murray, 76; Dorwin Stoddard, 76; and Phyllis Scheck, 79.

In another development, a second man, who was sought by Arizona and federal authorities, has been cleared of any involvement in the shooting.

The man was a cab driver who drove the gunman to the grocery store outside of which the shooting occurred, the Washington Post reported, quoting Pima County Sheriff's Deputy Jason Ogan as saying.

Handout photo of Jared Loughner, suspected in the shooting of a federal judge, congresswoman and others in Arizona on Saturday. [Xinhua]