The weekend attack on Rep. Gabrielle Giffords (D) of Arizona stunned her colleagues on Capitol Hill, prompting calls for more civil discourse and a suspension of legislative business this week.

Saturday’s shootings at a “Congress on Your Corner” event at a Safeway in Tucson was a stark reminder of the risks of public life. The US Capitol significantly upgraded security after the 9/11 attacks and the anthrax attacks at the Capitol 34 days later.

But when members meet with constituents back in their home districts, they are outside that security network – and only rarely with security provided by US Capitol Police. backing.

“An attack on one who serves is an attack on all who serve,” House Speaker John Boehner said Sunday. “All of us in our current roles in public service know that it comes with a risk. No act, however heinous, must be allowed to stop us from our duty.”

Mr. Boehner, who has been speaker for five days, called for flags to be flown at half staff in honor of Gabe Zimmerman, Representative Giffords’ director of community outreach, who was killed at the scene along with five others, including federal district judge John Roll and nine-year-old Christina-Taylor Green.

House majority leader Eric Cantor (R) of Virginia, in a statement released last Saturday, announced that all legislation scheduled to be considered this week, including a vote to repeal the health-care reform law, is postponed “so that we can take whatever actions may be necessary in light of today’s tragedy.”

The US Capitol Police declined to comment on the incidence of past threats to members of Congress or on plans for their security. “We don’t discuss security or statistics publicly,” said Sgt. Kimberly Schneider, a spokeswoman for the US Capitol Police in a phone interview. But she confirmed that the force has 1,800 sworn police officers who “do at times travel with member of Congress.”

“We give advice to members of Congress regarding prudent measures for their security,” she said.

FBI Director Robert Mueller, speaking at a Pima County Sheriffs Department briefing on Sunday, said, “We will do everything we can to ensure that our elected officials and the citizens we serve are safe.”

On its website, Fox News quoted a Republican aide as saying that law enforcement officials so far have only warned lawmakers to exercise increased awareness of potential threats following Saturday’s attack.

“I think the general mood is that this person was severely deranged and doesn’t signal some larger threat to members,” the aide was quoted as saying. “Anyone in public life gets threats at some point.”

Members of Congress are famously reluctant to appear to be setting up walls between themselves and their constituents. After three Puerto Rican separatists fired on the House floor on March 1, 1954, wounding five House members, the House considered erecting a glass wall around the visitors’ gallery, but lawmakers rejected it.

“Most members thought that it was a very bad idea, and that representatives of the people can’t become a guarded class of people,” says Raymond Smock, former House historian and director of the Robert C. Byrd Center for Legislative Studies in Shepherdstown, West Virginia.

The killing of two Capitol Police officers by a lone gunman on July 24, 1998, prompted significant security upgrades in the US Capitol, including authorization of a $100 million Capitol Visitor Center to allow underground screening before visitors enter the Capitol. After the 2001 attacks, lawmakers expanded security to authorize even more significant upgrades to the Visitor Center at a final cost of $621 million.

The only member of Congress to be have been shot and killed in office was Rep. Leo Ryan (D) of California, who was ambushed on a mission to investigate human rights violations in an American cult that had relocated to Guyana on Nov. 18, 1978, in what became known as the Jonestown Massacre. (The House historian’s office also notes that Delegate Jose Francisco Chaves of New Mexico was murdered by an unknown assailant on Nov. 26, 1904.)

Rep. Jackie Speier (D) of California, a staff aide shot with Ryan in 1978, survived the ambush to later become his replacement as representative for California’s 12th district. In an interview with ABC News on Saturday, she urged Congress not to step up security for members at home. “I certainly don’t want to have to be required to have a police presence,” she said. “If that’s the case, then it’s time for me to no longer be a congressmember.”

“This is not simply an attack on Ms. Giffords. This is an attack on democracy itself, on the ability ... to peaceably assemble, to come together to talk to one another,” said Democratic Whip Steny Hoyer (D) of Maryland, on CBS’s Face the Nation on Sunday.

"We are in a dark place in this country right now, and the atmospheric condition is toxic ... and much of it originates here in Washington, DC," said Emanuel Cleaver (D) of Missouri, speaking on NBC's New's "Meet the Press."

Sen. Jon Kyl (R) of Arizona cautioned against speculation on what motivated the shooter. “It’s probably giving him too much credit to ascribe a coherent political philosophy to him,” he said on CBS’s “Face the Nation” on Sunday. “I would just note, Gabrielle Giffords, a fine representative from Tucson, I think would be the first to say don’t rush to judgment here.”

“She meets constituents all the time. And she would not want to be restrained in any way from her ability to do that,” he added.

Giffords, who survived a tough reelection bid last year, made a point of being visible and available to constituents. On her way to the Jan. 8 event at which she was shot, Congresswoman Giffords tweeted: “My 1st Congress on Your Corner starts now. Please stop by to let me know what is on your mind or tweet me later.”

In last Thursday’s first-ever floor reading of the US Constitution, Giffords read the First Amendment: "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances."