Shortly before United Airlines Flight 93 crashed in southwestern Pennsylvania, a passenger told his wife the plane had been hijacked -- and that he was going to do something about it.

In his phone call, passenger Thomas Burnett told his wife, Deena, "I know we're all going to die -- there's three of us who are going to do something about it." Then, Burnett told his wife, "I love you, honey" and the call ended, the family's priest, the Rev. Frank Colacicco, told the San Francisco Chronicle.

It wasn't clear what caused the plane to go down when it did or whether the passengers had any effect.

Several people were able to make calls from the plane before the Boeing 757 slammed into a grassy field about 80 miles southeast of Pittsburgh. Rescue crews who reached the scene shortly after 10 a.m. found a deep V-shaped gouge filled with smoldering rubble. Forty-five people had been on board.

"We're being hijacked!" one man repeatedly told dispatchers who answered 911 lines before the plane crashed in western Pennsylvania.

Tuesday's hijacking was the last of four closely timed terrorist attacks, following the two crashes into New York's World Trade Center towers and a third into the Pentagon.

U.S. officials told The Associated Press on condition of anonymity that the Secret Service had alerted the White House that the hijackers may have been headed for Camp David, the presidential retreat in Maryland. Fearing the White House might be a target, the Secret Service diverted President Bush, who had been in Florida, to Louisiana and then Nebraska.

Flight 93 left Newark at 8:01 a.m. EDT headed for San Francisco. As it approached Cleveland, radar showed the plane banked left and headed back toward southwest Pennsylvania. Cleveland Mayor Michael R. White had said that air traffic controllers said they could hear screaming on a plane they communicated with.

On board, flight attendant CeeCee Lyles grabbed her cell phone and call her husband and four sons in Fort Myers, Fla.

"She called him and let him know how much she loved him and the boys," said her aunt, Mareya Schneider. During the call, he heard people screaming in the background, Schneider said.

In California, Alice Hoglan picked up her phone about 9:45 EDT to the hear the voice of her son, Mark Bingham, 31.

"He said, 'I want you to know I love you very much. I'm calling you from the plane. We've been taken over. There are three men that say they have a bomb," Hoglan said. The phone went dead a short time later.

The caller who reached emergency dispatchers said he was inside a locked bathroom on the plane.

Dispatcher Glenn Cramer said the man repeatedly said, "We're being hijacked!" and that his call was not a hoax.

"He heard some sort of explosion and saw white smoke coming from the plane and we lost contact with him," Cramer said. The man never identified himself.

Tuesday night, FBI agents and forensic archeologists began picking through tiny pieces of rubble. Neither the cockpit voice recorder nor the flight data recorder had been recovered, and it was expected to be days before the victims could be identified.

In Pennsylvania's Richland Township, Cambria County, on Tuesday morning, police Chief Jim Mock said air traffic control coordinators reported a large aircraft heading toward the John Murtha Johnstown Cambria County Municipal Airport. The controllers said the aircraft would not identify itself.

Minutes later, the plane crashed in rural Somerset County, about 20 miles away.

"It was like an atomic bomb hit," said John Walsh, 72, who heard the crash and drove to the site while still in his bathrobe. "When I got there, the plane was obliterated. You couldn't see the cockpit or the wings or nothing."

Mark Stahl was listening to reports about the World Trade Center attacks on the radio when he heard Flight 93 crash. In nearby Shanksville, the crash sent people running to their doors, and the fire whistles began blowing.

"I didn't know what to think," Stahl said. "It was shocking."

United CEO James Goodwin said the airline was sending a team to Pennsylvania to assist the investigation and provide assistance to family members. United said it had identified all passengers and crew and was notifying families. No names were released immediately.

"Today's events are a tragedy and our prayers are with everyone at this time," Goodwin said.