House Republicans suspended their work this week, including a much-anticipated vote on Obamacare, in response to the shooting rampage in front of a Tucson, Ariz., supermarket that left six people dead and Democratic Rep. Gabrielle Giffords clinging to life. In a conference call with House Democrats and Republicans, Majority Leader Eric Cantor, R-Va., said he was canceling the regular schedule, including the Wednesday ballot on a bill to repeal the health care reform law.

Instead, Cantor said, the House on Wednesday would take up a resolution honoring the shooting victims and Giffords, 40, who was sworn in to a third term just days ago and had been holding a "Congress on Your Corner" event with constituents in front of a supermarket when she was shot in the head from two feet away.

President Obama on Sunday ordered that American flags at all federal buildings be flown at half-staff and called for a nationwide moment of silence at 11 a.m. Monday, which the president will mark at a ceremony on the South Lawn of the White House.

There was no word on whether Obama planned to go to Arizona, but he postponed a trip to New York scheduled for Tuesday.

Charges are expected to be filed against Jared Lee Loughner, 22, the suspected gunman whose Internet postings include indecipherable rants against the government but who appears to have no direct connection to any political group. Police identified, interviewed and cleared a second man originally thought to be a potential accomplice. He was a cab driver who dropped Loughner off at the event.

Giffords remains in critical condition, in a medically induced coma at University Medical Center in Tucson. Doctors said they were worried about swelling in her brain and bone fragments causing complications, but optimistic about Giffords' chances of recovery. The bullet appeared to have pierced the left lobe of her brain and exited out the front of her skull, which could mean less brain damage and a better recovery, they said.

Giffords is responding to simple commands such as hand squeezes, another positive sign of recovery, doctors said.

"Overall this is about as good as it's going to get," Dr. Peter Rhee, the hospital's chief trauma surgeon, told reporters Sunday.

The conference call for House members included more than 800 people as staff and lawmakers' families listened in. One participant said it was a "very bipartisan" conference devoid of the attacks that have marked the deteriorating relationship between the two parties as recently as last Friday, when they fought bitterly on the House floor over health care repeal.

House Speaker John Boehner, R-Ohio, told those on the call that he had ordered the House sergeant at arms, U.S. Capitol Police and FBI to hold "an in-depth security overview" for lawmakers on Wednesday. Another briefing will be held for district office directors, who often meet with constituents on behalf of lawmakers.

"Yesterday was a grim day for our institution and our country," Boehner said on the call. "Gabby was attacked while doing the most fundamental duty of a member of Congress, listening to her constituents."