-- Gerry McCarty lost 70 friends in the World Trade Center attacks on Sept. 11, 2001, and to this day, the former New York City police officer cannot travel past Ground Zero.

"I don't go down there," he said Sunday, visibly steeling himself for questions he'd rather not contemplate. "I don't drive by. I don't walk by."

For each of the three previous anniversaries, when thousands have gathered at the site in Lower Manhattan to memorialize nearly 3,000 victims, McCarty stayed away.

"In those 29 minutes, I lost more friends and family than in all my 52 years," he said. "I've seen death. Close friends of mine in the police department have been killed. But it was one at a time and they were doing what they chose to do."

His eyes moisten. A quintessential Irishman -- tough on the outside, marshmallow soft inside -- he is embarrassed.

Sunday, McCarty marked the four-year anniversary of the worst terrorist attack in U.S. history by helping with the rescue and recovery effort in a disaster of similar magnitude. Though Hurricane Katrina ultimately may not claim as many lives as the 2001 attacks, the storm and its aftermath have wrought far greater damage on New Orleans and the Gulf Coast.

"I have to remember them the way I lived and worked with them, and that's what I am doing here today," he said.

At precisely 9:28 a.m. Central time Sunday -- the moment that the World Trade Center's North Tower collapsed four years ago -- McCarty stood in a cramped meeting room on the eighth floor of City Hall listening to his boss, John "Patch" Paczkowski. The pair arrived here Sunday with a small contingent from the emergency management office of the Port Authority of New York and New Jersey to help New Orleans leaders regroup and rebuild.

"We feel a very special kinship with the people of New Orleans," Paczkowski told a few dozen New Orleans emergency response officials. "We can't imagine the level of devastation that has hit your city."

Across the nation and around this devastated city, thousands paid tribute Sunday to the Sept. 11 victims and the as yet untold number of people lost to Katrina. At a memorial service in New Orleans's Algiers neighborhood, firefighters from New York and their colleagues here shared the pain and frustration wrought by Katrina.

The Montgomery County Fire and Rescue Service on Sunday morning presented New York firefighters a Montgomery County flag that flew over their encampment at the Pentagon after the Sept. 11 attacks. The flag was signed by about 100 Montgomery County police officers, firefighters and emergency medical personnel who were in New Orleans assisting in the aftermath of Hurricane Katrina, said Pete Piringer, spokesman for the fire department.

Here, in the makeshift emergency operations center, the tribute was brief, almost antiseptic. Paczkowski said a few words, presented a Port Authority flag to a few New Orleans officials and half-jokingly declared: "Back to work."

Reflecting for too long hurts too much.

"That was harder than I thought it was going to be," Paczkowski, 51, said as he slipped into an adjacent office. "Every day at the Port Authority, we're thinking we could be a target again. We're reliving 9/11 in our minds every day."

Paczkowski, too, has skipped the "mega memorials" each Sept. 11 in favor of a simple church service with family.

"It's too much for me," he said. Fifteen of his friends, including the best friend he was scheduled to have coffee with that morning, perished in the disaster. He and five others trapped in an elevator dangling near the 50th floor were lucky to escape, prying open the elevator door with the handle of a window washer's squeegee and carving their way out through a sheetrock wall with its blade.

Like the Marine he once was, Paczkowski wears his hair short and kept his emotions in check Sunday -- until he was asked how his wife reacted to the prospect of him coming to New Orleans.

"Nine-eleven really changed our lives," he said, eyes welling with tears. In the four years since the Port Authority's trade center offices were wiped out, "she doesn't like to see me go to work."

Many of the emergency personnel said they found solace in helping New Orleans recover from the sort of disaster they understand all too well. "I can't think of a better place to be to help people who went through the same things," said Carl Lindgren, deputy coordinator of the Arlington Office of Emergency Management.

"It does help to be engaged and productive and helping people," Paczkowski said. "It is therapy, in a way."

Lindgren has been urging local city employees to take some time to process the horror of the past two weeks. If they do not, Lindgren warns: "You may get through this incident, but it may be the end of your career."

Lindgren, who oversaw one of the triage centers for people critically wounded at the Pentagon, attended a memorial on the one-year anniversary of the attacks, then packed up the tributes, plaques and T-shirts he had received for his valor.

In the New Orleans emergency operations center, McCarty has the title of chief of staff. Seated in a corner, jotting in a notebook, he looks out at the collection of disaster veterans from New York, Los Angeles, Arlington and now New Orleans. The scene is all too reminiscent of the day four years ago when the twin towers fell.

"I see familiar faces in all of these faces," he said. "I see them on the street. I see them everywhere."

New York firefighter Gerard Gorman prays alongside others in a ceremony marking the fourth anniversary of the Sept. 11 attacks while working in hurricane-ravaged New Orleans.New York firefighters working in New Orleans mark the fourth anniversary of the Sept. 11, 2001, attacks at Our Lady of Holy Cross College.New York firefighter Regina Wilson sings "Amazing Grace" at a ceremony.