Wearing a tan prison uniform, Jared Loughner, 22, was brought into the heavily guarded Phoenix courtroom in handcuffs. His head was shaved and a cut was visible on his right temple.
Hours earlier, the nation paused for a moment of silence in honor of the victims of Saturday's mass shooting in Tucson, Ariz. As hundreds of people lined up outside the U.S. Capitol for the silent tribute, President Barack Obama and the first lady bowed their heads and stood silent outside the White House.
The president plans to travel to Tucson on Wednesday and will likely attend a memorial service for the victims, CNN and The Associated Press reported.
U.S. Rep. Gabrielle Giffords, the apparent main target of the shootings, was shot in the head during the rampage and remained in critical condition today. Her husband, a top astronaut due to command the final U.S. space shuttle mission, spoke out for the first time since his wife's shooting, saying there's little left to do "but pray."
The father of the youngest shooting victim called for the death sentence for the gunman.
"It's a fairly clear-cut case, and I'm a fan of capital punishment in this regard," John Green, whose 9-year-old daughter, Christina, was killed, told CBS's "The Early Show."
Astronaut Mark Kelly issued his first statement late Sunday, a day after his wife was shot while meeting with constituents outside a supermarket.
"Many of you have offered help. There is little that we can do but pray for those who are struggling," Kelly said in a statement posted on Giffords' congressional website. "If you are inspired to make a positive gesture, consider two organizations that Gabby has long valued and supported: Tucson's Community Food Bank and the American Red Cross."
Kelly, 46, made no mention of his wife's medical condition, but doctors have said they are "cautiously optimistic" that Giffords will survive. The 40-year-old three-term Democrat, who was shot in the head, remains in critical condition in a medical coma and on a ventilator. Doctors say she has responded to simple commands and has even managed to give a thumbs-up sign.
"Gabby was doing what she loved most -- hearing from her constituents -- when this tragedy occurred," Kelly said in his statement. "Serving Southern Arizonans is her passion, and nothing makes her more proud than representing them in Congress."
In April, Kelly is slated to command what's expected to be the last space shuttle flight before the entire fleet retires. But it's too soon to tell whether he'll back out of the high-profile Endeavour mission to stay at his wife's bedside. His identical twin, Scott, is also an astronaut, currently following news of his family's crisis from thousands of miles up in space, aboard the International Space Station.
"I want to thank everyone for their thoughts and prayers, words of condolences and encouragement for the victims and their families of this horrific event," Scott Kelly wrote on Twitter from space.
"My sister-in-law, Gabrielle Giffords, is a kind, compassionate, brilliant woman, loved by friends and political adversaries alike -- a true patriot," he wrote. "What is going on in our country that such a good person can be the subject of such senseless violence? It's a sad day."
This isn't the first time family tragedy has touched the International Space Station. At Christmas 2007, astronaut Daniel Tani was aboard the orbiter when he learned of his mother's death in a car and train collision. Tani has been working at Mission Control in Houston this past week and has been in touch with Scott Kelly and other members of the space station crew, The Associated Press reported.
Loughner was charged Sunday with one count of attempted assassination of a member of Congress, two counts of killing an employee of the federal government and two counts of attempting to kill a federal employee. More charges are expected as well. Among those killed Saturday were a federal judge and a congressional aide.
A high-profile public defender, Clarke, has been appointed to represent Loughner. Clarke previously defended Kaczynski and assisted in the case of confessed al-Qaida operative Zacarias Moussaoui.
Friends and acquaintances described Loughner as a pot-smoking loner who lived with his parents and was kicked out of community college recently. College classmates and teachers said he was apt to burst out laughing hysterically at inappropriate times and made bizarre comments that seemed disjointed and out of context.
Saturday isn't believed to be the first time the suspect had contact with Giffords. When authorities searched his parents' home, they discovered a letter locked in a safe there, believed to be a form letter Giffords sent constituents as a thank-you for attending another meet-and-greet event in 2007.
"Also recovered in the safe was an envelope with handwriting on the envelope stating, 'I planned ahead' and 'my assassination' and the name 'Giffords,' along with what appears to be Loughner's signature," authorities said.