President Obama to Attend Ariz. Memorial for Tucson Shooting Victims

VIDEO: After a moment of silence, government officials discuss toning down the rhetoric.
WATCH Tucson Tragedy Brings Unity to Capitol Hill

President Obama and first lady Michelle Obama are planning to go to Tucson, Ariz., Wednesday to attend a memorial service for the victims of Saturday's shooting spree that killed six people and injured 14, including Rep. Gabrielle Giffords.

The visit, first disclosed by a senior administration official to ABC News' Jake Tapper, was confirmed by the University of Arizona.

"President Obama will speak at a memorial event at 6 p.m. Wednesday, Jan. 12 to support and remember victims of the mass shooting in Tucson, and to lift the spirits of those who have been personally affected by this tragedy," the university said in a statement. "'Together We Thrive: Tucson and America,' will take place at McKale Center and is free and open to the campus and greater Tucson community."

The memorial in Tucson comes after the president and first lady led a national moment of silence this morning in Washington to honor the victims as Congressional business paused.

The president stood at the top of the driveway on the South Lawn of the White House to remember the victims. About 200 to 300 staffers gathered to observe the moment of silence, which lasted slightly more than a minute.

"Obviously all of us are still grieving and in shock from the tragedy that took place. Gabby Giffords and others are still fighting to recover, families are still absorbing the enormity of their losses," Obama said at the top of his joint remarks with French President Nicholas Sarkozy. "Right now, the main thing we're doing is offering our thoughts and prayers to those who have been impacted."

The Supreme Court began arguments 10 minutes earlier to take part in the national moment of silence. At the start of the arguments, Chief Justice John Roberts said the court was going to join the nation in stopping to consider the "senseless shooting on Saturday" that caused "devastating injury to persons who, all in their own way, contribute to the strength of our nation."

Roberts made special mention of U.S. District Judge John McCarthy Roll, 63, who was appointed by President George H.W. Bush in 1991, and was shot and killed Saturday while visiting the event being held by Giffords outside a Safeway.

The killing spree by alleged shooter Jared Loughner, 22, shocked the nation and has put on hold much of the business in Washington.

It was likely to overshadow Vice President Joe Biden's trip to Afghanistan, and Sarkozy's visit to Washington, D.C., today. Sarkozy met with Obama to discuss global economic issues and security.

On Capitol Hill, members have amped up precautionary measures.

The House delayed its scheduled agenda for this week, including the controversial bill slated for Wednesday that called for the repeal of the health care bill, a hot button issue that has triggered fiery debates in town hall meetings.

Instead, the House will convene that day to pass a resolution honoring Giffords and victims of the shooting.

"An attack on one who serves is an attack on all who serve. This is a time for the House to pull together as an institution -- one body, unified in our common purpose of serving the American people and fighting for the freedom and justice guaranteed to all by our Constitution," House Speaker John Boehner, R-Ohio, said Sunday in a bi-partisan conference call.

"What is critical is that we stand together at this dark time as one body," he added. "We need to rally around our wounded colleague, the families of the fallen, and the people of Arizona's 8th District. And, frankly, we need to rally around each other."

The Capitol Police has beefed up security on Capitol Hill and across the country, members of Congress say they are taking extra precautions amid fear of copycat attacks.

Shooting in Arizona Puts House Business on Hold

In a bipartisan move that hasn't been seen in some time, Boehner and House minority leader Nancy Pelosi, D-Calif., held a conference call to brief members on the Arizona shooting and the Congressional response.

Members were reminded to take common-sense precautions and inform local law enforcement of their events.

At least two members of Congress, Heath Shuler, D-N.C., and Jason Chaffetz, R-Utah, say they're not taking any chances. The two told Politico they'll be packing guns when in public in their home districts.

There will be another bi-partisan security briefing on Capitol Hill by the Capitol Police, Sergeant-at-Arms and the FBI when members of Congress return Wednesday.

Doctors are hopeful that Giffords, who remains in intensive care, will recover and say that she is responding to basic commands, but they caution that the 40-year-old is not yet completely out of the woods.

Loughner, who was charged on four counts Sunday, will make his first court appearance in Phoenix today in front of Magistrate Judge Lawrence Anderson.

The president has been careful not to ascribe any political motive to the killings, instead cautioning against doing so. This weekend, Obama spoke to Giffords family as well as the family of Gabe Zimmerman, the congresswoman's 30-year-old employee who died on Saturday. A 9-year-old girl born on the day of the Sept. 11, 2001 terrorist attacks was also killed.

ABC News' Ariane de Vogue, Jonathan Karl and Jake Tapper contributed to this report.