PHOENIX (AP) – A 22-year-old man described as a social outcast with wild beliefs steeped in mistrust faces a federal court hearing on charges he tried to assassinate a U.S. congresswoman in a Tucson shooting rampage that left six people dead.

A federal judge, a congressional aide and a young girl were among the six people killed, while Rep. Gabrielle Giffords and 13 others were injured in the bursts of gunfire outside a Tucson supermarket.

Public defenders are asking that the attorney who defended Oklahoma City bombing conspirator Timothy McVeigh and “Unabomber” Ted Kaczynski defend Jared Loughner, who makes his first court appearance Monday at 2 p.m. MST (2100 GMT).

Sheriff Clarence Dupnik said Loughner was not cooperating and told ABC News the suspect had said “not a word” to investigators. Dupnik said authorities were all but certain Loughner acted alone, saying “he’s a typical troubled individual who’s a loner.”

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The hearing in Phoenix comes just a few hours after President Barack Obama leads a shocked and saddened nation in a moment of silence for the victims and their families. Obama will observe the moment of silence at 11 a.m. EST (1600 GMT) with White House staff on the South Lawn.

Those killed included U.S. District Judge John Roll, 63, and 9-year-old Christina Taylor Green, who was born on Sept. 11, 2001, and was featured in a book called “Faces of Hope” that chronicled one baby from each state born on the day terrorists killed nearly 3,000 people in the U.S.

Others killed were Giffords aide Gabe Zimmerman, 30; Dorothy Morris, 76; Dorwin Stoddard, 76; and Phyllis Schneck, 79.

As authorities filed the charges against Loughner Sunday, they alleged he scrawled on an envelope the words “my assassination” and “Giffords” sometime before he took a cab to a shopping center where the congresswoman was meeting with constituents Saturday morning.

Giffords, 40, lay in intensive care at a Tucson hospital, after being shot in the head at close range. Doctors said she had responded repeatedly to commands to stick out her two fingers, giving them hope she may survive.

Neurosurgeon Dr. Michael LeMole of Tucson’s University Medical Center, appearing Monday on CBS television, said, “the best way to describe her this morning is that she’s holding her own.”

LeMole said he removed a portion of her skull in order to perform the surgery but likely will replace it at some point.

“We don’t close the book on recovery for years,” he said, “so it’ll take as long as it takes. I think the real question will be how long it will take before she’s out of the woods.”

About 200 people gathered outside Giffords’ Tucson office Sunday evening for a candlelight vigil. Earlier in the day, people crammed the synagogue where Giffords has been a member, as well as the Mountain Avenue Church of Christ, which lost one member in the attack and saw another one wounded.

Authorities weren’t saying late Sunday where Loughner was being held, and officials were working to appoint an attorney for him. Heather Williams, the first assistant federal public defender in Arizona, said they’re asking that San Diego attorney Judy Clarke be appointed.

Clarke is a former federal public defender in San Diego and Spokane, Washington. She served on teams that defended McVeigh, a co-conspirator in the 1995 bombing of a federal building in Oklahoma that killed 168 people; Kaczynski, whose mail bombs killed three and injured 23 others over two decades; and Susan Smith, a South Carolina woman who drowned her two sons in 1994.

Loughner is charged 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.

Discoveries at Loughner’s home in southern Arizona, where he lived with his parents in a middle-class neighborhood lined with desert landscaping and palm trees, have provided few answers to what motivated him.

Court papers filed with the charges said he had previous contact with Giffords. The documents said he had received a letter from the Democratic lawmaker in which she thanked him for attending a “Congress on your Corner” event at a mall in Tucson in 2007.

Comments from friends and former classmates bolstered by Loughner’s own Internet postings have painted a picture of a social outcast with almost indecipherable beliefs steeped in mistrust and paranoia.

“If you call me a terrorist then the argument to call me a terrorist is Ad hominem,” he wrote Dec. 15 in a wide-ranging posting.

Two high school friends said they had fallen out of touch with Loughner and last spoke to him around March, when one of them was going to set up some bottles in the desert for target practice and Loughner suggested he might come along. It was unusual — Loughner hadn’t expressed an interest in guns before — and his increasingly confrontational behavior was pushing them apart. He would send bizarre text messages, but also break off contact for weeks on end.

“We just started getting sketched out about him,” the friend said.

Around the same time, Loughner’s behavior also began to worry officials at Pima Community College, where Loughner began attending classes in 2005, the school said in a release.

Between February and September, Loughner “had five contacts with PCC police for classroom and library disruptions,” the statement said. He was suspended in September after college police discovered a YouTube video in which Loughner claimed the college was illegal according to the U.S. Constitution.

He withdrew voluntarily the following month, and was told he could return only if, among other things, a mental health professional agreed he did not present a danger, the school said.

Police said he purchased the Glock pistol used in the attack in November.

An official familiar with the shooting investigation said Sunday that local authorities were looking at a possible connection between Loughner and an online group known for white supremacist, anti-immigrant rhetoric.

The official, who spoke on condition of anonymity to discuss the ongoing investigation, said local authorities were examining the American Renaissance website for possible motives.

The group’s leaders said in a posting on their website that Loughner never subscribed to their magazine, registered for any of the group’s conferences or visited their Internet site.

Giffords, a conservative Democrat re-elected in November, faced threats and heckling over her support for immigration reform and the health care overhaul. Her office was vandalized the day the House approved the landmark health care measure.

It was not clear whether those issues motivated the shooter to fire on the crowd gathered to meet Giffords.

Copyright 2011 The Associated Press.