NEW ORLEANS — New Orleans turned much of its attention Sunday to gathering up and counting the dead across a ghastly landscape awash in perhaps thousands of corpses. "It is going to be about as ugly of a scene as I think you can imagine," the nation's Homeland Security chief warned.

As authorities struggled to keep order, police shot eight people, killing five or six, after gunmen opened fire on a group of contractors traveling across a bridge on their way to make repairs, authorities said.

Air and boat crews searched flooded neighborhoods for survivors, and federal officials urged those still left in New Orleans to leave for their own safety.

To expedite the rescues, the Coast Guard requested through the media that anyone stranded hang out brightly colored or white linens or something else to draw attention. But with the electricity out though much of the city, it was not known if the message was being received.

With large-scale evacuations completed at the Superdome and Convention Center, the death toll was not known. But bodies were everywhere: floating in canals, slumped in wheelchairs, abandoned on highways and medians and hidden in attics.

"I think it's evident it's in the thousands," Health and Human Services Secretary Mike Leavitt said Sunday on CNN, echoing predictions by city and state officials last week. The U.S. Public Health Service said one morgue alone, at a St. Gabriel prison, expected 1,000 to 2,000 bodies.

In the first official count in the New Orleans area, Louisiana emergency medical director Louis Cataldie said authorities had verified 59 deaths — 10 of them at the Superdome.

"We need to prepare the country for what's coming," Homeland Security Secretary Michael Chertoff said on "Fox News Sunday." "We are going to uncover people who died, maybe hiding in houses, got caught by the flood. . . . It is going to be about as ugly of a scene as I think you can imagine."

Chertoff said rescuers have encountered a number of people who said they did not want to evacuate.

"That is not a reasonable alternative," he said. "We are not going to be able to have people sitting in houses in the city of New Orleans for weeks and months while we de-water and clean this city. . . . The flooded places, when they're de-watered, are not going to be sanitary."

Evacuations continued late Sunday as Coast Guard helicopters picked up refugees from a dry stretch of I-10 where they had been dropped off by rescue boats.

"We're not satisfied to leave, but they say it's going to be three or four months, so we need to go somewhere where we can have a life," said Tommy McDaniel, 38.