Pat Burns, center, of Tucson, stands with friends outside the offices of U.S. Rep. Gabrielle Giffords, D-Ariz., during a candlelight vigil for Giffords, Saturday, Jan. 8, 2011 in Tucson, Ariz. Giffords was shot in the head earlier in the day during a speech at a local supermarket. (AP Photo/Matt York)
Candles, flowers and signs are shown outside the offices of U.S. Rep. Gabrielle Giffords, D-Ariz., during a candlelight vigil for Giffords Saturday, Jan. 8, 2011 in Tucson, Ariz. Giffords was shot in the head earlier in the day during a speech at a local supermarket.
(AP Photo/Matt York)
Ian Anderson, right, and Rob Servis, of Tucson, stand outside the offices of U.S. Rep. Gabrielle Giffords, D-Ariz., during a candlelight vigil for Giffords Saturday, Jan. 8, 2011 in Tucson, Ariz. Giffords was shot in the head earlier in the day during a speech at a local supermarket. (AP Photo/Matt York)
Hundreds gather for a vigil at the Arizona Capitol for Rep. Gabrielle Giffords, Saturday, Jan. 8, 2011, in Phoenix. Rep. Gabrielle Giffords of Arizona was shot in the head Saturday by a gunman who opened fire outside a grocery store during a meeting with voters, killing a federal judge and four others in a rampage that rattled the country and left politicians fearful for their safety. (AP Photo/Ross D. Franklin)
As she wipes away tears, Balbir Grewal joins hundreds who gather for a vigil at the Arizona Capitol for Rep. Gabrielle Giffords, D-Ariz., Saturday, Jan. 8, 2011, in Phoenix. Rep. Gabrielle Giffords of Arizona was shot in the head Saturday by a gunman who opened fire outside a grocery store during a meeting with voters, killing a federal judge and four others in a rampage that rattled the country and left politicians fearful for their safety. (AP Photo/Ross D. Franklin)
Don Bivens, center, chairman of the Arizona Democratic Party, his wife Trish Refo, and their son Andrew Bivens, 10, join hundreds who gathered for a vigil at the Arizona Capitol for Rep. Gabrielle Giffords, D-Ariz., Saturday, Jan. 8, 2011, in Phoenix. Rep. Gabrielle Giffords of Arizona was shot in the head Saturday by a gunman who opened fire outside a grocery store during a meeting with voters, killing a federal judge and four others in a rampage that rattled the country and left politicians fearful for their safety. (AP Photo/Ross D. Franklin)
Cruz Clark-Yost, 5, of Phoenix, center, looks at his candle as he is joined by his mother Ruth Clark, right, and the family dog, Max, as they join hundreds who gathered for a vigil at the Arizona Capitol for Rep. Gabrielle Giffords, D-Ariz., Saturday, Jan. 8, 2011, in Phoenix. Rep. Gabrielle Giffords of Arizona was shot in the head Saturday by a gunman who opened fire outside a grocery store during a meeting with voters, killing a federal judge and four others in a rampage that rattled the country and left politicians fearful for their safety. (AP Photo/Ross D. Franklin)
People gather outside University Medical Center for a prayer vigil for Rep. Gabrielle Giffords, Saturday, Jan. 8, 2011 in Tucson, Ariz. Rep. Gabrielle Giffords of Arizona was shot in the head Saturday by a gunman who opened fire outside a grocery store during a meeting with voters, killing a federal judge and four others in a rampage that rattled the country and left politicians fearful for their safety. (AP Photo/The Arizona Republic, David Kadlubowski)
People gather for a vigil at University Medical Center for US Representative Gabrielle Giffords (D-AZ), who was in critical condition after being shot in the head by a gunman in Tucson, Arizona, in an attack which killed six including a federal judge and a nine-year-old girl. (AFP/Getty Images/Laura Segall)