A 22-year-old man accused of trying to assassinate a US congresswoman and killing six other people has appeared in court.
Jared Loughner, who appeared with a shaved head and a cut on his right temple, stared vacantly into the packed courtroom as he attended a short procedural hearing in Phoenix.
Representative Gabrielle Giffords lay about a 100 miles away in an intensive care unit, gravely wounded after being shot through the head but able to give a thumbs-up sign that doctors found as a reason to hope.
Thirteen other people were injured in the bursts of gunfire outside an Arizona supermarket.
The shootings, which claimed the lives of six people, including a federal judge, a congressional aid and a nine-year-old girl, have dominated news in the US, prompting outrage and sparking debate over gun control and whether heated political rhetoric fuelled the incident.
Before the hearing began, Jared Loughner's court-appointed lawyer Judy Clarke whispered to the defendant, who only spoke to say "yes" when the judge asked if he understood that he could face life in prison or the death penalty if convicted.
Ms Clarke had earlier defended "Unabomber" Ted Kaczynski and al Qaida operative Zacarias Moussaoui among others.
The judge ordered Loughner to be held without bail.
President Barack Obama is to travel to Arizona to attend a memorial service for the victims, a senior administration official said.
Earlier, Americans observed a moment of silence for the victims of the rampage, from the South Lawn of the White House and the steps of the US Capitol to legislature beyond Arizona and the International Space Station.