The nation reeled in horror and seethed in anger Tuesday as knife-wielding terrorists hijacked four passenger jets and steered three of them into the Twin Towers of New York's World Trade Center and the Pentagon in Washington.
Thousands were feared dead in New York, and up to 800 were killed in the nation's capital.
In a day of infamy being compared to the Dec. 7, 1941, attack on Pearl Harbor, the Twin Towers crashed to the ground about an hour after passenger airliners smashed into each of the 110-story buildings at 8:45 a.m. and 9:03 a.m. EDT Tuesday.
Forty minutes after the second New York crash, another airliner smashed into the side of the Pentagon. The nerve center of the American military continued to burn well into the night.
A fourth hijacked aircraft crashed seven minutes later, at 9:50 a.m. in western Pennsylvania. A Virginia congressman said that plane was intended to crash into the presidential retreat at Camp David, Md.
President Bush, in a nationally broadcast address from the Oval Office at 8:30 p.m. EDT, said "thousands of lives were suddenly ended" through "evil, despicable acts of terror" and vowed to "find those responsible and bring them to justice."
The president said the United States would retaliate against "those behind these evil acts," and any country that harbors them. "Today, our nation saw evil," Bush said.
U.S. officials began piecing together a case linking terror mastermind Usama bin Laden to the attack almost immediately, aided by an intercept of communications between his supporters and harrowing cell phone calls from victims aboard the jetliners before they crashed. Authorities were focusing some of their efforts on possible bin Laden supporters in Florida based on the identification of a suspected hijacker on one of the manifests of the four jets that crashed, law enforcement sources said.
The sources said the FBI was preparing to search locations in Broward County in south Florida and Daytona Beach in central Florida. U.S. intelligence also intercepted communications between bin Laden supporters discussing the attacks on the World Trade Center in New York and the Pentagon, according to Utah Sen. Orrin Hatch.
"They have an intercept of some information that included people associated with bin Laden who acknowledged a couple of targets were hit," Hatch said in an interview with The Associated Press. He declined to be more specific.
Thousands of rescue workers in New York and Washington were searching for survivors among the rubble left by Tuesday's terror attacks.
Officials refused to give figures but said as many as several thousand could be dead in the New York City attacks, after both towers of the World Trade Center collapsed. Solid casualty figures might not come for weeks, officials warned.
Tuesday night, an unconfirmed report of an explosives-filled van heading toward Manhattan added to the chaos.
The four airliners that were hijacked had 266 people aboard alone and there were no known survivors. The Arlington County, Va., fire chief said deaths at the Pentagon ranged between 100 and 800.
A New York City Fire Department union official said he feared 300 firefighters who first reached the scene had died in rescue efforts at the trade center — where 50,000 people worked — and dozens of police officers were missing.
"The number of casualties will be more than most of us can bear," a visibly distraught Mayor Rudolph Giuliani warned Tuesday evening.
Police sources said some people trapped in the Twin Towers managed to call authorities or family members and that some trapped police officers made radio contact. In one of the calls, which took place in the afternoon, a businessman phoned his family to say he was trapped with policemen, whom he named, the source said.
Meanwhile, U.S. law enforcement and intelligence agencies were said to be focusing their efforts almost exclusively on Usama bin Laden as the culprit behind the attacks. Bin Laden, the fugitive Saudi billionaire who has lived in Afghanistan the last several years, had recently warned of massive attacks against the United States.
Unconfirmed reports coming from Boston said police there had identified several men believed to be supporters of bin Laden. Among them were trained pilots and several man who had traveled to Boston from Maine in the hours before the attacks.
Officials believe only those with some detailed pilot training could have succeeded in their suicide mission of flying the planes into the trade center and the Pentagon, as they did the previous morning.
According to reports, at least one Middle Eastern student at Embry-Riddle University in Daytona Beach, Fla., a flight school, was missing as of last night. Authorities were looking into reports he may have been on one of the hijacked planes.
In New York, more than 1,000 people were undergoing treatment at hospitals, with 200 in critical condition. Another 1,600 "walking wounded" were treated at Liberty State Park in New Jersey. Police Commissioner Bernard Kerik said rescuers had already determined there were some people alive in two buildings downtown.
Late in the afternoon, Building 7, an evacuated, 47-story part of the World Trade Center complex, collapsed after burning out of control for eight hours.
Authorities went on alert from coast to coast, evacuating high-profile buildings and tightening security at strategic installations. For the first time in history, all air traffic was stopped throughout the U.S.
The Navy dispatched ships to New York Harbor to assist in the rescue and to ward off any possible further attacks. Two aircraft carriers — the USS John F. Kennedy and the USS George Washington — were ordered to leave port in Norfolk, Va., so they would not become targets.
"The Pentagon is functioning. It will be in business tomorrow," said Defense Secretary Donald Rumsfeld in an evening briefing at the Pentagon.
Officials speculated about the timing of the attack.
In June, a U.S. judge had set this Wednesday as the sentencing date for a bin Laden associate for his role in the 1998 bombing of a U.S. embassy in Tanzania that killed 213 people. The sentencing had been set for the federal courthouse near the World Trade Center.
Abdel-Bari Atwan, editor of the al-Quds al-Arabi newspaper, said he received a warning from Islamic fundamentalists close to bin Laden, but did not take the threat seriously. "They said it would be a huge and unprecedented attack but they did not specify," Atwan said in a telephone interview in London.
In the evening, in a bipartisan display of unity, members of both the Senate and House of Representatives convened on the steps of the Capitol to offer their full support to the president and U.S. military forces in their efforts to track down and punish the terrorists.
House Speaker Dennis Hastert, R-Ill., said it was still not clear who was responsible, "but we have our suspicions."
"And when that is justified ... we will act," he said. "We will stand with this president ... and we will stand as Americans together throughout this time."
The lawmakers then sang "God Bless America."
Evacuations were ordered at the United Nations in New York and at the Sears Tower in Chicago. Los Angeles mobilized its anti-terrorism division, and security was intensified around the naval installations in Hampton Roads, Va. Walt Disney World in Orlando, Fla., was evacuated and closed, as were Mount Rushmore, Seattle's Space Needle and the Gateway Arch in St. Louis. Major League Baseball cancelled its entire Tuesday and Wednesday schedules.
"This is the second Pearl Harbor. I don't think that I overstate it," said Sen. Chuck Hagel, R-Neb.
In Lima, Peru, Secretary of State Colin Powell cut short his first official visit to South America to return home. "A terrible, terrible tragedy has befallen my nation, but it has befallen all those who believe in democracy," Powell told the Organization of American States.
Key indexes sank on world stock markets and some European airlines canceled flights to the United States and recalled planes already in the air. Trading on Wall Street was suspended.
The people aboard planes who managed to make cell phone calls each described similar circumstances: They indicated the hijackers were armed with knives, in some cases stabbing flight attendants. They then took control of the planes and aimed them at their targets.
The two flights that toppled the World Trade Center took off 15 minutes apart from Boston's Logan International Airport.
The first crash was a hijacked American Airlines plane that smashed into the World Trade Center at 8:45 a.m. It was identified as Flight 11, a Boeing 767 en route to Los Angeles. There were 81 passengers, nine flight attendants and two pilots aboard the flight.
A second plane, United Airlines Flight 175 to Los Angeles, crashed into the World Trade Center 18 minutes later. The Boeing 767 carried 56 passengers, two pilots and seven flight attendants.
A second American plane, Flight 77 from Dulles, Va., to Los Angeles, a Boeing 757, crashed into the Pentagon at 9:43. There were 58 passengers, four flight attendants and two pilots aboard. Fox News commentator Barbara Olson, a former congressional staffer and Republican activist, was on the plane. Officials said she made two phone calls to her husband, Solicitor General Ted Olson, from her cell phone before the crash. Olson told her husband that the plane had been hijacked by terrorists wielding "knife-like" instruments.
In Pennsylvania, United Airlines Flight 93, a Boeing 757 en route from Newark, N.J., to San Francisco, crashed at 9:50 a.m. about 80 miles southeast of Pittsburgh. Rep. James Moran, D-Va., said that plane was apparently intended for Camp David, the presidential retreat in the mountains of Maryland. The crash site was 85 miles northwest of Camp David.
An emergency dispatcher in Westmoreland County, Pa., received a cell phone call from a man who said he was a passenger locked in the bathroom of United Flight 93, said dispatch supervisor Glenn Cramer.
"We are being hijacked, we are being hijacked!" Cramer quoted the man as saying. The man told dispatchers the plane "was going down. He heard some sort of explosion and saw white smoke coming from the plane and we lost contact with him," Cramer said.
In New York, the planes blasted fiery, gaping holes in the upper floors of the Twin Towers. A witness said he saw bodies falling and people jumping out. About an hour later, the southern tower collapsed with a roar and a huge cloud of smoke; the other tower fell about a half-hour after that.
Donald Burns, 34, who had been at a meeting on the 82nd floor of One World Trade Center, saw four severely burned people on the stairwell. "I tried to help them but they didn't want anyone to touch them. The fire had melted their skin. Their clothes were tattered," he said.
People ran down the stairs in panic and fled the building. Thousands of pieces of what appeared to be office paper drifted over Brooklyn, about three miles away.
Several subway lines were immediately shut down. New York's mayoral primary election was postponed. All bridges and tunnels into Manhattan were closed down.
By early afternoon, the downtown area was cordoned off and a rescue effort was under way. Hundreds of volunteers and medical workers converged on triage centers, offering help and blood. Paramedics waiting to be sent into the rubble were told that "once the smoke clears, it's going to be massive bodies," said Brian Stark, a former Navy paramedic who volunteered to help.
The Associated Press contributed to this report.