The US government charged a 22-year-old man with attempted assassination of a congresswoman on Sunday while doctors expressed optimism that the wounded lawmaker, Gabrielle Giffords, would recover.
The shootings of Giffords and 19 other people - six of whom were killed - in Tucson on Saturday fueled debate about extreme political rhetoric in the United States after an acrimonious campaign for congressional elections in November.
The US government charged Jared Lee Loughner with two counts of first degree murder, one count of attempted assassination and two other counts of attempted murder.
Investigators said in the charges they found an envelope at his residence with the handwritten phrases "I planned ahead" and "My assassination," along with the name "Giffords" and what appeared to be Loughner's signature.
The suspect opened fire with a semi-automatic pistol at point-blank range outside a supermarket. The FBI said it had cleared a man officials had earlier sought to locate in connection with the shootings.
On Monday, President Barack Obama presided over a national moment of silence for severely injured Giffords and those killed. On the White House South Lawn, Obama was joined by first lady Michelle Obama and White House staff members on a cold morning.
The moment was marked at the US Capitol and elsewhere around a nation still coming to grips with the tragedy.
Hero woman hailed
US authorities hailed as a hero a woman, Patricia Maisch, who stopped a rampage by a gunman by physically confronting him as he attempted to reload his emptied handgun.
"This lady was standing in line to have her picture taken with Gabrielle when all hell broke loose," Pima County sheriff Clarence Dupnik said.