The bloodbath ended with the gunman committing suicide, bringing the death toll to 33 and stamping the campus in the picturesque Blue Ridge Mountains with unspeakable tragedy, perhaps forever.
Investigators gave no motive for the attack. The gunman's name was not immediately released, and it was not known whether he was a student.
"Today the university was struck with a tragedy that we consider of monumental proportions," Virginia Tech President Charles Steger said. "The university is shocked and indeed horrified."
But he was also faced with difficult questions about the university's handling of the emergency and whether it did enough to warn students and protect them after the first burst of gunfire. Some students bitterly complained they got no warning from the university until an e-mail that arrived more than two hours after the first shots rang out.
Wielding two handguns and carrying multiple clips of ammunition, the killer opened fire about 7:15 a.m. on the fourth floor of West Ambler Johnston, a high-rise coed dormitory, then stormed Norris Hall, a classroom building a half-mile away on the other side of the 2,600-acre campus. Some of the doors at Norris Hall were found chained from the inside, apparently by the gunman.
Two people died in a dorm room, and 31 others were killed in Norris Hall, including the gunman, who put a bullet in his head. At least 15 people were hurt, some seriously. Students jumped from windows in panic.
Alec Calhoun, a 20-year-old junior, said he was in a 9:05 a.m. mechanics class when he and classmates heard a thunderous sound from the classroom next door - "what sounded like an enormous hammer."
Screams followed an instant later, and the banging continued. When students realized the sounds were gunshots, Calhoun said, he started flipping over desks for hiding places. Others dashed to the windows of the second-floor classroom, kicking out the screens and jumping from the ledge of Room 204, he said.
"I must've been the eighth or ninth person who jumped, and I think I was the last," said Calhoun, of Waynesboro, Va. He landed in a bush and ran.
Calhoun said that the two students behind him were shot, but that he believed they survived. Just before he climbed out the window, Calhoun said, he turned to look at the professor, who had stayed behind, perhaps to block the door. The instructor was killed, he said.
At an evening news conference, Police Chief Wendell Flinchum refused to dismiss the possibility that a co-conspirator or second shooter was involved. He said police had interviewed a male who was a "person of interest" in the dorm shooting who knew one of the victims, but he declined to give details.
"I'm not saying there's a gunman on the loose," Flinchum said. Ballistics tests will help explain what happened, he said.
Sheree Mixell, a spokeswoman for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, said the evidence was being moved to the agency's national lab in Annandale. At least one firearm was turned over, she said.
Mixell would not comment on what types of weapons were used or whether the gunman was a student.
Young people and faculty members carried out some of the wounded themselves, without waiting for ambulances to arrive. Many found themselves trapped behind chained and padlocked doors. SWAT team members with helmets, flak jackets and assault rifles swarmed over the campus. A student used his cell-phone camera to record the sound of bullets echoing through a stone building.
Trey Perkins, who was sitting in a German class in Norris Hall, told The Washington Post that the gunman barged into the room at about 9:50 a.m. and opened fire for about a minute and a half, squeezing off about 30 shots.
The gunman first shot the professor in the head and then fired on the students, Perkins said. The gunman was about 19 years old and had a "very serious but very calm look on his face," he said.
"Everyone hit the floor at that moment," said Perkins, 20, of Yorktown, Va., a sophomore studying mechanical engineering. "And the shots seemed like it lasted forever."
Erin Sheehan, who was also in the German class, told the student newspaper, the Collegiate Times, that she was one of only four of about two dozen people in the class to walk out of the room. The rest were dead or wounded, she said.
She said the gunman "was just a normal-looking kid, Asian, but he had on a Boy Scout-type outfit. He wore a tan button-up vest, and this black vest, maybe it was for ammo or something."
Students said that there were no public-address announcements after the first shots. Many said they learned of the first shooting in an e-mail that arrived shortly before the gunman struck again.
"I think the university has blood on their hands because of their lack of action after the first incident," said Billy Bason, 18, who lives on the seventh floor of the dorm.
Steger defended the university's conduct, saying authorities believed that the shooting at the dorm was a domestic dispute and mistakenly thought the gunman had fled the campus.
"We had no reason to suspect any other incident was going to occur," he said.
Steger emphasized that the university closed off the dorm after the first attack and decided to rely on e-mail and other electronic means to spread the word, but said that with 11,000 people driving onto campus first thing in the morning, it was difficult to get the word out.
He said that before the e-mail went out, the university began telephoning resident advisers in the dorms and sent people to knock on doors. Students were warned to stay inside and away from the windows.
"We can only make decisions based on the information you had at the time. You don't have hours to reflect on it," Steger said.
Some students and Laura Wedin, a student programs manager at Virginia Tech, said their first notification came in an e-mail at 9:26 a.m., more than two hours after the first shooting.
The e-mail had few details. It read: "A shooting incident occurred at West Amber Johnston earlier this morning. Police are on the scene and are investigating." The message warned students to be cautious and contact police about anything suspicious.
Edmund Henneke, associate dean of engineering, said that he was in the classroom building and that he and colleagues had just read the e-mail advisory and were discussing it when he heard gunfire. He said that moments later SWAT team members rushed them downstairs, but that the doors were chained and padlocked from the inside. They left the building through an unlocked construction area.
Until Monday, the deadliest shooting in modern U.S. history was in Killeen, Texas, in 1991, when George Hennard plowed his pickup truck into a Luby's Cafeteria and shot 23 people to death, then himself.
The massacre Monday took place almost eight years to the day after the Columbine High bloodbath near Littleton, Colo. On April 20, 1999, two teenagers killed 12 fellow students and a teacher before taking their own lives.
Previously, the deadliest campus shooting in U.S. history was a rampage in 1966 at the University of Texas at Austin, where Charles Whitman climbed the clock tower and opened fire. He killed 16 people before police shot him.
Founded in 1872, Virginia Tech has more than 25,000 full-time students, it has the state's largest full-time student population. It is best known for its engineering school and its powerhouse Hokies football team.
The campus is centered on the Drill Field, a grassy field where military cadets practice. The dorm and the classroom building are on opposites sides of the Drill Field.
President Bush offered his prayers to the victims and the people of Virginia, saying the tragedy would be felt in every community in the country.
After the shootings, all campus entrances were closed, and classes were canceled through Tuesday. The university set up a spot for families to reunite with their children. It also made counselors available and planned an assembly Tuesday.
Police said there had been bomb threats on campus over the past two weeks but said they had not determined a link to the shootings.
It was second time in less than a year that the campus was closed because of a shooting.
In August, the opening day of classes was canceled when an escaped jail inmate allegedly killed a hospital guard off campus and fled to the Tech area. A sheriff's deputy was killed just off campus. The accused gunman, William Morva, faces capital murder charges.
Among Monday's dead was Ryan Clark, a student from Martinez, Ga., with several majors who carried a 4.0 grade-point average, said Vernon Collins, coroner in Columbia County, Ga.
At a hastily arranged service Monday night at Blacksburg Presbyterian Church, the Rev. Susan Verbrugge gazed out at about 150 bowed heads.
"Death has come trundling into our life, a sudden and savage entity laying waste to our hearts and making desolate our minds," Verbrugge said during a prayer. "We need now the consolation only you can give."
After the service, Clark's friend Gregory Walton, a 25-year-old who graduated last year, said he feared his nightmare had just begun.
"I knew when the number was so large that I would know at least one person on that list," said Walton, a banquet manager. "I don't want to look at that list. I don't want to.
"It's just, it's going to be horrible, and it's going to get worse before it gets better."