SHANKSVILLE, Pa. -- Homes shook and the earth trembled as United Airlines Flight 93 roared out of the sky and slammed into the soft earth of a former strip mine near this small town on Sept. 11, 2001.

Many of those first to respond to the scene were surprised to find no corpses, no obvious wreckage -- only a smoking crater, singed trees and an eerie silence that made it seem at first as if there had been no plane at all.

It's been five years since passengers and crew members battled hijackers in the skies over Pennsylvania. But eyewitnesses, family members and first responders say images from that day are seared in their memories -- even if most of the horror was left to their imagination.

State police Lt. Patrick Madigan, the former station commander of the Somerset County barracks, was watching TV broadcasts of the terrorist attacks in New York and Washington, D.C, in the moments before Flight 93 went down.

"Well, at least there's no terrorist targets in Somerset County," he remembers telling a colleague.

Seconds later, the phone rang and a 911 dispatcher in Westmoreland County reported that a plane with a bomb on board was over Somerset County. Then a call came in from one of Lt. Madigan's troopers: He had just heard an explosion so violent it shook his home.

Soon phones at the barracks were ringing off the hook. Lt. Madigan and other troopers rushed to the scene, an open field bounded by woods on the site of a former strip mine.

"My first thought was, where's the plane crash?" says Lt. Madigan, now 53. "All there was was a hole in the ground and a smoking debris pile."

But troopers soon began finding small but identifiable pieces of a commercial aircraft and bits of the United Airlines in-flight magazine. They quickly realized there would be no survivors.

Rick King, 42, of Shanksville, was behind the wheel of the first firetruck to arrive at the crash scene, showing up before the state police, FBI and other federal investigators.

The former assistant chief of the Shanksville volunteer fire department had heard Flight 93 scream overhead, seen a massive fireball light up the sky and felt an explosion rock the entire town of Shanksville.

"It was a pretty scary time," he says. "I just remember driving down the road, wondering what we were about to see."

But besides a burning landing-gear tire, smoldering branches in the nearby woods and a few brush fires, there was little to indicate a jetliner had just crashed, he says.

"Where is this plane? And where are the people?" Mr. King remembers thinking as he stepped off the truck.

There were thousands of tiny pieces scattered around -- bits of metal, insulation, wiring -- but no fuselage, no wings, only a smoking crater and charred earth.

"It will always be part of our town," he says.

State police Maj. Frank Monaco remembers the crash site as a "smoking hole in the ground."

"It didn't look like a plane crash," says Maj. Monaco, 56, from New Kensington.

The plane had burrowed into the soft, reclaimed earth of the former strip mine and crumpled like an accordion, he says.

Maj. Monaco quickly went about securing the scene, registering the hordes of investigators and first responders, and shooing away onlookers.

"It was a real three-ring circus around there," he says.

But what stands out as much in his mind as the chaos of the first few days is the kindness of local residents. They brought food and water to investigators and opened their homes for them to wash and nap after sometimes 12-hour shifts.

"They treated us like family members," Maj. Monaco says. "If they were going away for the day, they'd say, 'Here's the key to the house.' How do you thank someone for something like that?

Veteran FBI agent Michael Soohy had been to airplane crash scenes before, and he thought he knew what to expect: chaos, bodies, a hulking wreck of a jet.

"I don't think anyone expected to see what they didn't see," said the 50-year-old who grew up near Johnstown. "It's almost like a dart hitting a pile of flour. ... The plane went in, and the stuff back-filled right over it."

And the sheer number of local police, volunteer firefighters and paramedics at the scene worried him.

"Everyone within 30-40 miles of that place responded," Mr. Soohy said. "It was so chaotic the first two hours, I thought, 'My God, what a mess this is going to be.' "

But within only a few days, the jurisdictional issues that sometimes plague investigations had disappeared, he said. State, local and federal agencies -- along with residents and businesses -- were cooperating better than he thought possible.

"It was just one of those things that you don't experience too often," he said. "There were church groups making food for us and bringing it out, and I mean good food."

Somerset County Coroner Wallace Miller had never handled a case with more than two deaths. On Sept. 11, he had to process 44 bodies -- or at least what little was left of them.

"We only recovered about 8 percent of potential remains," he says. "Most of the material was vaporized."

But from the fragments of bodies recovered from the site, Mr. Miller and other investigators were able to identify everyone on Flight 93: four hijackers and 40 passengers and crew.

The remains of the hijackers were handed over to the FBI, and those of the passengers and crew were returned to families in caskets or cremated.

"Nobody had any formula. We did what we did. Hopefully it turned out all right," Mr. Miller says.

He says it still seems strange to him that events of such historic importance transpired in this remote, rural area.

"This could have occurred anywhere," he says. "This just happened to be the place where it happened."

Paul Bomboy, 39, of Hooversville, was at the Somerset County library installing a satellite connection so visitors could see news about jets slamming into the World Trade Center and the Pentagon.

That's when Mr. Bomboy, an avid volunteer and information technology director at a local coal company, heard that a plane had crashed in nearby Shanksville. He rushed to the scene in his capacity as commander of the Hooversville Rescue Squad.

"I realized very early in the game that there was no paramedic work needed there," he says. "I imagined a place, I didn't see a place, I saw a hole. ... There weren't bodies."

Changing hats, he used coal company equipment to help set up a command center at a nearby warehouse for the scores of first responders, police and federal investigators who were arriving.

"This is a county that pulls together," he says. "When something happens, people that don't even talk to each other come out of the woodwork and work together."

Terry Butler was taking parts off scrapped cars at a salvage yard near Shanksville when he saw a plane flying unusually fast and low over the nearby hills.

"It started to go up a little bit, made a right turn and came down," says Mr. Butler, 45, of Somerset.

Then Mr. Butler heard a loud explosion and felt the ground shake beneath his feet as the plane crashed into a field about a mile away.

"I didn't believe it at first. I was just in shock," Mr. Butler says.

Since that day, he says, he's had trouble sleeping.

Sitting at her desk at Shanksville-Stonycreek High School, Principal Constance Hummel suddenly heard an explosion and felt the floor beneath her rumble.

"Looking back, two things always stick out in my mind," says Ms. Hummel, 55, who retired last September after 32 years at the school. "That's the moment all the people in that plane died. .... And the second thought is, that it could have been the school."

Soon she was receiving calls from teachers about tiles shaken from classroom ceilings and smoke rising over the playground.

Flight 93 had crashed about a mile from the school, and investigators later told Ms. Hummel that the plane might have hit the school had it crashed a few seconds later.

"We didn't lose any lives, our homes weren't taken. But what we lost in Shanksville was our innocence," Ms. Hummel says. "You worry about your children and your grandchildren, the kind of world they'll be living in."

Donna Glessner heard the explosion, too, from her home a few miles from the disaster site.

"They must be dropping bombs on all the world if they're dropping bombs on Shanksville," she remembers thinking.

In the months that followed, visitors arrived in droves at the open fields where Flight 93 had crashed. Some took pictures and videos of a nearby pond, assuming it to be the crater left by the downed plane.

It wasn't. Investigators had already filled it in. But there was no one to tell the visitors where the jetliner had gone down.

So in January 2002, Ms. Glessner brought together a group of volunteers, known now as the Flight 93 ambassadors, to point visitors to the crash site and to describe what happened aboard the plane on Sept. 11.

Forty-five volunteers now take turns working two-hour shifts each day at the Flight 93 Memorial. Some months they guide more than 25,000 visitors.

"You feel like you're really meeting a need," Ms. Glessner says. "People who come to the memorial are so curious and anxious to understand what happened there."

Allison Vadhan, 43, of Atlantic Beach, N.Y., lost her mother, Kristin White-Gould, on Flight 93.

About a week after the disaster, she and other family members were bused to the site. Rescue workers, state troopers and others lined the road to offer their condolences.

"It was scary to look at and horrible to imagine what happened to everybody, what happened to that big plane," she says. "It was all left to our imagination, and maybe that's for the best."

She was also struck by the quiet, rolling hills and the beauty of the surrounding farms and mountains.

On the eve of the five-year anniversary, she says, "I find that each year it gets easier and I'm able to deal with it better and brace myself and protect myself for the big day."

But she worries about her son and what the future may hold for his generation.

"He's going to have to live with this problem even more than we are," Ms. Vadhan says. "This problem is not going away."