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[Updated at 10:30 p.m. ET] A man who helped subdue the gunman in Saturday's Arizona shooting spree said the man was trying to reload when he was tackled to the ground.

"He was ready for war. He was not playing around," Joe Zamudio told CNN. "He was going to keep shooting. It was not over. He had just ran out of bullets."

The gun, which another bystander had wrestled from the gunman, was empty and cocked open, and the shooter had another magazine at the ready, Zamudio said.

Zamudio pinned him to the ground until police showed up. The suspect, 22-year-old Jared Lee Loughner, is in custody of the Pima County Sheriff's Office, and authorities are obtaining search warrants for a residence and his vehicle. Authorities also are seeking a person of interest but his suspected connection to the incident is unclear.

Loughner is accused of shooting 18 people, including U.S. Rep. Gabrielle Giffords, a third-term Democrat who had organized the "Congress on Your Corner" meet and greet. Authorities believe the gunman had specifically targeted Giffords. She is in critical condition after undergoing surgery for a single gunshot wound to the head, but doctors said they are optimistic over her prospects for recovery.

Watch a timeline of events

Eleven others were wounded in the shooting and six are dead, among them U.S. District Court Judge John Rolls, a friend of Giffords' who had stopped by the event to say hello after attending Mass, Pima County Sheriff Clarence Dupnik said.

Also killed was Giffords staffer Gabe Zimmerman, director of community outreach who had coordinated the event to introduce Giffords to her constituents.

A 9-year-old girl also was killed.

The shooting sent shock waves through Washington, where Giffords was regarded as gracious and kind, a moderate Democrat known for her dedication to her constituents and willingness to work across party lines.

In light of the shootings, all legislation on the House schedule for the coming week has been postponed, House Majority Leader Eric Cantor announced in a statement.

Americans also struggled to come to terms with the event. Many of them showed up to a vigil at the Arizona State Capitol to pray together and share their thoughts.

In the Twitterverse, theories abounded as to the gunman's motivation. Meanwhile, while speaking to the press , the sheriff lamented "the vitriolic rhetoric" in American political discourse, suggesting it played a role in the shooting.

"This has not become the nice United States of America that most of us grew up in and I think its time we do the soul-searching," he said.

"The anger, the hatred the bigotry that goes on in this country is getting to be outrageous and unfortunately, Arizona has become the capital. We have become the mecca of prejudice and bigotry."

[Updated at 10:00 p.m. ET] A House vote scheduled for Monday on whether to repeal health care legislation has been postponed after Saturday's shooting.

All legislation on the House schedule for the coming week has been postponed in a decision by leaders of both political parties in the House so "we can take whatever actions may be necessary in light of today's tragedy," House Majority Leader Eric Cantor said in a statement.

Read more on CNN.com

[Updated at 9:13 p.m. ET] Some who knew Giffords and others who just wanted an outlet for emotions in the wake of the shooting rampage gathered on Capitol Hill Saturday night to honor the victims.

More than 50 marchers braved subfreezing temperatures and gusty winds to march to the Capitol and up the west steps to hold the vigil.

Read more on CNN.com

[Updated at 8:55 p.m. ET] A  law enforcement source familiar with the investigation says the Glock model 19 used in the shootings was purchased legally. The official did not have details at this time as to when and where the gun was purchased.

The gun was loaded with a 30-round magazine. The official said it is likely the extended magazine used in the shooting  was purchased separately and at a different time. The official said such a magazine does not automatically come with a weapons purchase and that it would be extremely rare for them to be sold together in one purchase.

The official said the suspect had purchased another gun a few years ago but this person did not know the details about what happened to that weapon and if the alleged shooter still owned it.

[Updated at 8:23 p.m. ET] Officials are not convinced that the suspected gunman acted alone, Pima County Sheriff Clarence Dupnik told reporters.

Law enforcement is actively searching for a "person of interest" who is a white male in his 50s believed to have assisted the suspect in a shooting, Dupnik said.

A suspect who Dupnik would not name is in the custody of the Pima County Sheriff's Office, he said. The suspect has had previous contact with law enforcement "regarding threats" to kill, Dupnik said, and described him as having a "troubled past."

CNN has confirmed that the suspect's name is Jared Lee Loughner, 22, whose apparent online footprint professes an distrust of government and a fondness for books such as "Mein Kampf," "The Communist Manifesto," "Peter Pan" and "The Republic."

"There's reason to believe this individual has a mental issue and I think that people who are unbalanced are especially susceptible to vitriol," he said.

"Vitriol" in public debate was a recurring theme in Dupnik's remarks as he blasted the media for "the vitriolic rhetoric" heard on television and radio.

[Updated at 7:57 p.m. ET] Gabe Zimmerman, director of community outreach for U.S. Rep. Gabrielle Giffords, was among those killed in Saturday's shooting at a constituents meeting outside a Tucson Safeway, Gifford press secretary CJ Karamargin said.

Zimmerman was the staff member who set up today’s event in Giffords’ district, Karamargin said. The Tucson native was engaged to be married.

[Updated at 7:43 p.m. ET] The Army said in a statement that the suspect in the shooting was never in the Army.

"He attempted to enlist in the Army but was rejected for service.  In accordance with the Privacy Act, we will not discuss why he was rejected," the Army said in a statement.

[Updated at 7:21 p.m. ET] Jared Lee Loughner, the suspect, had a limited presence on social-media sites, including YouTube and MySpace. Here's a sampling of some of the messages that CNN found on Loughner's pages:

MySpace

December 26, 2010: I'm not going to change the mistakes, you don't know – funny! (I think the CIA watches my-space)

December 30, 2010: I now understand a certain word - Cult!

YouTube

December 15, 2010: If I define terrorist then a terrorist is a person who employs terror or terrorism, especially as a political weapon.

I define terrorist.

Thus a terrorist is a person who employs terror or terrorism, especially
as a political weapon.

If you call me a terrorist then the argument to call me a terrorist is Ad hominem.

You call me a terrorist.

Thus the argument to call me a terrorist is Ad hominem.

December 15, 2010: The majority of citizens in the United States of America have never read the United States of America's Constitution.

You don't have to accept the federalist laws.

Nonetheless, read the United States of America's  Constitution to apprehend all of the current treasonous laws.

You're literate, listener?

Read more about Loughner's digital footprint on CNN.com

[Updated at 7:12 p.m. ET] The University of Arizona's men's basketball game against Stanford University has been postponed following the shootings.

"The University feels the game should be delayed with deep respect to the victims and families impacted by this tragedy," Arizona athletics director Greg Byrne said.

The game will be played at 12:30 p.m. MST Sunday.

[Updated at 6:48 p.m. ET] Saturday's deadly shootings at an Arizona constituency meeting outside a Tucson Safeway appear to have “no nexus to terrorism," a law enforcement official said.

This official did not know if there had been any recent threat against Rep Giffords but said there are frequent threats to various members of Congress, mostly via phone  calls or e-mails, or mailed threats.

[Updated at 6:30 p.m. ET] U.S. Supreme Court Chief Justice John Roberts released this statement on the death of U.S. District Court Chief Judge John Roll, who was killed in the shootings:

"Chief Judge John Roll was a wise jurist who selflessly served Arizona and the nation with great distinction, as attorney and judge, for more than 35 years.  I express my deepest condolences to his wife Maureen and his children, as well as the other victims and their families.  Chief Judge Roll’s death is a somber reminder of the importance of the rule of law and the sacrifices of those who work to secure it."

[Updated at 6:16 p.m. ET] The Tea Party released this statement regarding the shootings:

“We at the Tea Party Express are shocked and saddened to hear about the terrible tragedy that took place in Tucson today. It is appalling that anyone would commit such unthinkable violence against Congresswoman Gabrielle Gifford, her staff, a sitting federal judge and the many other victims and families impacted.

"These heinous crimes have no place in America, and they are especially grievous when committed against our elected officials. Spirited debate is desirable in our country, but it only should be the clash of ideas.  An attack on anyone for political purposes, if that was a factor in this shooting, is an attack on the democratic process.  We join with everyone in vociferously condemning it."

Read the full story on CNN.com

[Updated at 5:41 p.m. ET] Who is Gabrielle Giffords? She's a Democrat who was first elected in 2006. She has served as chairwoman of the House Space and Aeronautics Subcommittee and also holds seats on the House Science and Technology and Armed Services committees.

She won her third term in a closely contested race against a Tea Party-sponsored candidate and was one of three Democratic legislators who reported vandalism at their offices following the March vote on health care reform.

She is married to Navy Capt. Mark Kelly, a NASA astronaut who is scheduled to lead a space shuttle mission to the International Space Station. The two married in 2007, after meeting four years prior in China, as young leaders selected by the National Committee on U.S.-China Relations, Giffords told the New York Times in her wedding announcement.

The article described their courtship as a drawn-out affair between two deeply committed civic servants who slowly found their way to each other. When they met, Giffords was seeing someone and Kelly was married.

After Giffords split from her boyfriend, she invited Kelly to join her on a tour of the Arizona State Prison in Florence.

"I’d been working on legislation dealing with capital punishment. Mark is the son of police officers — well, he just really wanted to sit in ‘the chair,' " she told the newspaper.

The two married three years later, they married at an organic produce farm in Amado, Arizona, called Agua Linda. An avid recycler, Giffords wore a Vera Wang gown borrowed from a friend.

"To a bride who moves at a velocity that exceeds that of anyone else in Washington, and a groom who moves at a velocity that exceeds 17,000 miles per hour," a wedding guest said in a toast to the couple.

[Updated at 5:20 p.m. ET] Arizona Gov. Jan Brewer expressed condolences for the shooting victims - 6 are dead and 12 injured.

"I am just heartbroken. Gabby (Giffords) is more than just a colleague she is a friend. She has always been a noble public servant," an emotional Brewer said, pausing for composure.

"I ask the people of Arizona and the people of America to keep the victims and their families in their prayers, and pray for their recovery and pray that in Arizona we never have to experience a tragedy like this ever again."

Giffords publicized the "Congress on Your Corner" meet-up at the Safeway in her southern Arizona district on her Twitter account.

Judge John Roll, the chief judge on the U.S. District Court for Arizona, was among 6 people killed, along with a 9-year-old girl, officials said.

Witnesses said the gunman shot Giffords at point blank range through the head and then continued firing. The suspect, identified by law enforcement sources as Jared Lee Loughner, has been taken into custody.

[Updated at 4:52 p.m. ET] Chief Judge John Roll was among 6 people killed at an Arizona constituent meeting outside a Tucson grocery store Saturday.

[Updated at 4:30 p.m. ET] The suspect in a shooting at an Arizona constituent meeting outside a Tucson grocery story is a white male born in 1988, CNN's Jeanne Meserve has confirmed from a federal law enforcement source.

Six people have died, including a 9-year-old girl, and 12 were injured, including U.S. Rep. Gabrielle Giffords, authorities said.

[Updated at 4:07 p.m. ET] Rep. Gabrielle Giffords is in critical condition and a young child has died after a shooting at a political meeting at an Arizona grocery store, a hospital spokesman said Saturday.

Giffords, who was hosting the event, is under anesthesia after undergoing surgery for a single gunshot wound to the head "through and through," said Dr. Peter Rhee, Trauma Director at the University Medical Center in Tucson.

"The Congresswoman is not deceased. She is in critical condition," Rhee said in a press conference. "I am very optimistic about recovery."

Giffords publicized the "Congress on Your Corner" meet-up at the Safeway in her southern Arizona district on her Twitter account.

[Updated at 3:40 p.m. ET] Six people have died and 12 - including U.S. Rep. Gabrielle Giffords - were injured in a shooting at a political meeting at a Tucson, Arizona, grocery store Saturday, according to Rick Kastigar of the Pima County Sheriff's Department.

[Updated at 3:20 p.m. ET] A suspect is in custody in the shootings of at least 12 people, including Rep. Gabrielle Giffords, at a constituent meeting at an Arizona grocery store, the U.S. Capitol Police said in a statement.

"The suspect is in custody. No further details on the motive or other victims are available at this time," the statement said. "The U.S. Capitol Police are directly involved in this investigation. As more information is developed, it will be provided. In the interim, all Members and staff are advised to take reasonable and prudent precautions regarding their personal security."

A statement from President Obama confirmed that some people had died.

"This morning, in an unspeakable tragedy, a number of Americans were shot in Tucson, Arizona, at a constituent meeting with Congresswoman Gabrielle Giffords.  And while we are continuing to receive information, we know that some have passed away, and that Representative Giffords is gravely wounded," he said.

"We do not yet have all the answers.  What we do know is that such a senseless and terrible act of violence has no place in a free society.  I ask all Americans to join me and Michelle in keeping Representative Giffords, the victims of this tragedy, and their families in our prayers."

[Updated at 3:00 p.m. ET] Rep. Gabrielle Giffords is currently undergoing surgery for a gunshot wound to the head, a spokeswoman for the University Medical Center in Tucson said.

Nine patients were brought to the hospital, including a child. All of them are in either serious or critical condition and are undergoing surgery, spokeswoman Darci Slaten said.

A federal judge was also among those shot, a law enforcement official said. It is not clear whether he was among those taken to the hospital.

[Updated at 2:43 p.m. ET] There were conflicting reports Saturday about the condition of U.S. Rep. Gabrielle Giffords following a shooting Saturday at a Tucson, Arizona, grocery store. Giffords' press secretary said the congresswoman remains in surgery for her injuries, disputing an earlier report from a law enforcement source saying she had died.

[Updated at 2:23 p.m. ET] U.S. Rep. Gabrielle Giffords died Saturday after a gunman opened fire at a Tucson, Arizona grocery store, a law enforcement source said. Giffords, who had been holding a meeting with constituents, was among at least 12 people shot.

[Updated at 1:51 p.m. ET] U.S. Rep. Gabrielle Giffords was among at least 12 people shot at a Tucson, Arizona, grocery store, a Democratic source told CNN's Dana Bash. The source called her injuries "pretty serious."

[Updated at 1:41 p.m. ET] U.S. Rep. Gabrielle Giffords was meeting with constituents at a Safeway grocery store in Tucson, Arizona, where at least 12 people were injured in a shooting shortly after 10 a.m. MST Saturday, a spokesman for the Pima County sheriff's Department said. It is unclear whether Giffords was among those hurt.

"Several" people were shot Saturday at a grocery store in Tucson,
Arizona, a spokesman for the Pima County Sheriff's Department said. No other details were immediately available.