LAS VEGAS — Smoke was still rising from the collapsed towers of the World Trade Center in New York when someone left a T-shirt, scrawled with a message of pain, on a railing near a faux fireboat in front of the New York-New York hotel-casino on the Las Vegas Strip.

Then another T-shirt appeared. And another.

"It was absolutely spontaneous. Someone just started doing it, and it just caught on," said David Schwartz, director of the Center for Gaming Research at the University of Las Vegas and curator of a collection that has grown to 5,422 T-shirts, hats and handwritten notes now kept at the school's library.

Thirty at a time are displayed these days in a permanent display case that casino owner MGM Resorts International opened in 2003, at the foot of the resort's scale model Statue of Liberty. An American flag hangs this weekend from the base of the statue, with the railing next to the display case draped with red, white and blue bunting.

"To our Brothers, who we have lost, May your Courage always be our strength," read one, from firefighters in the Pennsylvania town of Numidia.

Others were from FDNY Ladder 5 in New York City; Cincinnati; Cheektowaga Volunteer Hose Co. No. 1 near Buffalo, N.Y., and one signed with names from Chicago Fire Department Truck 22, Ambulance 31 and Engine 83.

"Los Sentimentos de dolor y alegra son universales," a firewoman from Huelva, Spain, wrote on another shirt. "The sentiments of pain and happiness are universal."

"It's sobering," Schwartz said of the collection. "And it's a reminder of the 3,000 people who lost their lives that day."

With solemnity and speeches, ceremonies are scheduled around Nevada this weekend to mark the 10th anniversary of the Sept. 11, 2001, terror attacks at the World Trade Center and the Pentagon in Washington, D.C., and the crash of hijacked United Flight 93 in Pennsylvania.

In Las Vegas, police and firefighters — including some wearing their usual 50 pounds of protective turnout gear — plan to climb 108 floors up the tallest casino building in Las Vegas: the Stratosphere casino tower. They'll also carry biographies and photos of the 343 firefighters and paramedics, 60 police officers and one police dog killed at the World Trade Center.

"We can never forget the day and the sacrifices that were made," said Mike Mossel, a Las Vegas firefighter and coordinator of the Sunday morning event — one of many being held around the country benefiting the National Fallen Firefighters Foundation.

From atop the 1,149-foot Stratosphere, participants would be able to see a nearby Econo Lodge motel in a low-rent part of the Strip where Mohamed Atta once stayed. He was the operational leader of the airline hijackings that led to the carnage in New York, Washington and Pennsylvania.

Investigators later determined that five hijackers — Atta and the pilots of each of the four hijacked aircraft — visited Las Vegas in the months before the attacks. The purpose for the trips into and out of Las Vegas was never fully determined. Investigators said they thought the men may have used the city as cover — to blend in among millions of tourists from all over the world.

In northern Nevada, Gov. Brian Sandoval planned to observe a moment of silence at a Reno Balloon Festival remembrance ceremony in Rancho San Rafael Park, and lay wreaths at the Law Enforcement Memorial at the Capitol grounds in Carson City and at the Firefighters Memorial in Mills Park.

Carson City's Memorial Ceremony at Mills Park will include the unveiling of an I-beam from the World Trade Center site. Sandoval also was scheduled in Fallon for an afternoon memorial near City Hall.

At Reno's Powning Veterans Memorial Park, the American Veterans Organization planned to take part in a nationwide bugle ceremony with the playing of "Taps" at 5:46 a.m., 6:37 a.m. and 7:03 a.m. to commemorate the moment planes crashed 10 years ago.

An annual tolling of the bells was scheduled at Las Vegas fire stations at 6:59 a.m., and a flag that once flew over the World Trade Center will be hoisted to half-staff at a fire station west of the Las Vegas Strip where a piece of steel from the fallen towers is displayed.

Clark County fire stations will sound alarms and sirens at 10 a.m.

Nevada Army and Air National Guard members were marking the anniversary by mourning the deaths of three colleagues who died Tuesday when a man opened fire inside a Carson City IHOP restaurant. They were among the four people killed and seven wounded.

The Guard was also remembering three members killed during deployments involving about 2,700 troops to Iraq and Afghanistan since the attacks. The Nevada Guard has 420 soldiers and airmen currently deployed in Afghanistan, Sgt. 1st Class Erick Studenicka said.

In downtown Las Vegas, tourists at the Fremont Street Experience casino pedestrian mall will be able to see a 2,500-pound steel beam fragment from ground zero. The Madame Tussauds wax museum will waive admission fees for active-duty firefighters, police and paramedics.

Las Vegas police and area firefighters will host a Sunday memorial at Police Memorial Park, and The Clark County Museum in Henderson will sound a Cold War-era air raid siren.

"Collectively we learned that you can't just think, 'It'll only happen to the other guy,'" said Bill Cassell, 59, a Las Vegas police officer who headed a search-and-rescue team that was deployed to New York. The team arrived at about the same time efforts at the World Trade Center rubble turned from rescue to recovery.

Cassell, now a police spokesman, was involved in planning the Las Vegas police ceremony.

Another member of the team, Terry Wilferd, 49, remembered having trouble reconciling the scene in front of him with his past experiences.

"Just absolute devastation," said Wilferd, a Henderson fire captain, SWAT team paramedic and former Air Force security police officer who served in the first Gulf War. "It was so far outside the norm that you just deal with what you can."

The married father of two remembered how thousands of people affected by the attacks were doing what they do every day when their lives changed forever.

Michael Wylie, 41, thought the same thing when he stopped Friday at the T-shirt memorial at the corner of Tropicana Avenue and Las Vegas Boulevard.

He considered the first responders who died. His children — a daughter now 9 and a son now 7 — are too young to remember the attacks 10 years ago.

"It makes you think. It really does," Wylie said before heading home to Muncie, Ind., and his job as an Indiana State Police sergeant. "They were just doing their jobs, going into the buildings."

Wylie recalled how after the attacks Americans rallied to help each other, and how patriotism bridged ideological differences. He said he teaches his children that Sept. 11 was a bad day, and that tolerance is important.

"Some people attacked us because they didn't like our freedoms, our beliefs and our way of doing things," Wylie said. "I learned to be aware of other people and their opinions and views."

"You don't have to agree with them," he said. "But you don't kill them, either."