TUSCON, Ariz. - (AP) - Federal prosecutors brought charges Sundayagainst the gunman accused of carrying out an assassination attempton Rep. Gabrielle Giffords and killing six people at a politicalevent in Arizona.

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Investigators said they carried out a search warrant at JaredLoughner's home and seized an envelope from a safe with messagessuch as "I planned ahead," "My assassination" and the name"Giffords" next to what appears to be the man's signature. Heallegedly purchased the Glock pistol used in the attack in Novemberat Sportsman's Warehouse in Tucson.

Court documents also show that Loughner had contact withGiffords in the past. Other evidence included a letter addressed tohim from Giffords' congressional stationery in which she thankedhim for attending a "Congress on your Corner" event at a mall inTucson in 2007.

Heather Williams, the first assistant federal public defender inArizona, says the 22-year-old suspect doesn't yet have a lawyer,but that her office is working to get a lawyer appointed forLoughner.

Loughner, 22, is accused of killing six people, including afederal judge, an aide to Giffords and a 9-year-old girl who wasborn on Sept. 11, 2001. Fourteen others were wounded, including thethree-term Democrat lawmaker. Authorities don't know his motive,but said he targeted Giffords at a public gathering around 10 a.m.Saturday outside a busy Tucson supermarket.

Doctors treating the Democrat provided an optimistic updateabout her chances for survival, saying they are "very, veryencouraged" by her ability to respond to simple commands alongwith their success in controlling her bleeding.

An unidentified man who authorities earlier said might haveacted as an accomplice was cleared Sunday of any involvement. PimaCounty sheriff's deputy Jason Ogan told The Associated Press onSunday that the man was a cab driver who drove the gunman to thegrocery store outside of which the shooting occurred.

One of the victims was Christina-Taylor Green, who was a memberof the student council at her local school and went to the eventbecause of her interest in government. She is the granddaughter offormer Philadelphia Phillies manager Dallas Green.

She was born on 9/11 and featured in a book called "Faces ofHope" that chronicled one baby from each state born on the dayterrorists killed nearly 3,000 people.

The fact that Christina's life ended in tragedy was especiallytragic to those who knew her. "Tragedy seems to have happenedagain," said the author of the book, Christine Naman. "In theform of this awful event."

Authorities said the dead included U.S. District Judge John M.Roll; Greene; Giffords aide Gabe Zimmerman, 30; Dorothy Morris, 76;Dorwin Stoddard, 76; and Phyllis Scheck, 79. Judge Roll had juststopped by to see his friend Giffords after attending Mass.

Arizona congresswoman shot, several killed in Tucson