BLACKSBURG, Va. - A gunman opened fire in a Virginia Tech dorm and then, two hours later, shot up a classroom building across campus Monday, killing 32 people in the deadliest shooting rampage in U.S. history. The gunman committed suicide, bringing the death toll to 33.

Students bitterly complained that there were no public-address announcements on campus after the first burst of gunfire. Many said the first word they received from the university was an e-mail more than two hours into the rampage around the time the gunman struck again.

Virginia Tech President Charles Steger said 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.

He defended the university's handling of the tragedy, saying: "We can only make decisions based on the information you had on the time. You don't have hours to reflect on it."

Investigators offered no motive for the attack. The gunman's name was not immediately released, and it was not known if he was a student.

The shootings spread panic and confusion on campus. Witnesses reporting students jumping out the windows of a classroom building to escape the gunfire. SWAT team members with helmets, flak jackets and assault rifles swarmed over the campus. Students and faculty members carried out some of the wounded themselves, without waiting for ambulances to arrive. A student used his cell-phone camera to record the sound of shots echoing through the stone classroom building.

The massacre took place at opposite sides of the 2,600-acre campus, beginning at about 7:15 a.m. at West Ambler Johnston, a coed dormitory that houses 895 people, and continuing at least two hours later at Norris Hall, an engineering building about a half-mile away, authorities said.

Two people were killed in a dormitory room, and 31 others were killed in the classroom building, including the gunman, police said.

"Today the university was struck with a tragedy that we consider of monumental proportions," Steger said. "The university is shocked and indeed horrified."

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 notify members of the university, but 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 to notify them and sent people to knock on doors to spread the word.

Virginia Tech Police Chief Wendell Flinchum would not say how many weapons the gunman carried. But a law enforcement official, speaking on condition of anonymity because the investigation was incomplete, said that the gunman had two pistols and multiple clips of ammunition.

Flinchum said that some doors in the classroom building had been chained shut from the inside.

Police said they were still investigating the shooting at the dorm when they got word of gunfire at the classroom building.

Some students bitterly questioned why the gunman was able to strike a second time.

"What happened today, this was ridiculous," student Jason Piatt told CNN. "While they send out that e-mail, 20 more people got killed."

Students and Laura Wedin, a student programs manager at Virginia Tech, said the first notification they got of the shootings 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.

Student Maurice Hiller said he went to a 9 a.m. class two buildings away from the engineering building, and no warnings were coming over the outdoor public address system on campus at the time.

Everett Good, junior, said of the lack of warning: "I'm trying to figure that out. Someone's head is definitely going to roll over that."

"We were kept in the dark a lot about exactly what was going on," said Andrew Capers Thompson, a 22-year-old graduate student from Walhalla, S.C.

At an evening news conference, the university president and police chief said they were still investigating whether the shootings at the dorm and the classroom building were related. But earlier in the day, the chief said he believed there was only one gunman, and he was dead.

Edmund Henneke, associate dean of engineering, said he was in the classroom building and he and colleagues had just read the e-mail advisory regarding the first shooting and were discussing it when he heard gunfire. He said moments later SWAT team members rushed them downstairs "but the doors were chained and padlocked from the inside." They left the building through a construction area that had not been locked.

Henneke said it is unfair to criticize the school over the delay in warning.

"People are absolutely making too much of that. You do what you can," Henneke said. "We have a huge campus. You have to close down a small town and you can't close down every way in or out."

At least 26 people were being treated at three area hospitals for gunshot wounds and other injuries, authorities said. Their exact conditions were not disclosed, but at least one was sent to a trauma center and six were in surgery, authorities said.

Up until Monday, the deadliest mass shooting in 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 that took place in 1966 at the University of Texas at Austin, where Charles Whitman climbed the clock tower and opened fire with a rifle from the 28th-floor observation deck. He killed 16 people before he was shot to death by police.

Founded in 1872, Virginia Tech is nestled in the Blue Ridge Mountains of southwestern Virginia, about 160 miles west of Richmond. With more than 25,000 full-time students, it has the state's largest full-time student population. The school is best known for its engineering school and its powerhouse Hokies football team.

The rampage took place on a brisk spring day, with snow flurries swirling around the campus. The campus is centered around the Drill Field, a grassy field where military cadets who now represent a fraction of the student body practice. The dorm and the classroom building are on opposites sides of the Drill Field.

A gasp could be heard at a campus news conference early in the day when the police chief announced that at least 20 people had been killed. Previously, only one person was thought to have been killed.

A White House spokesman said President Bush was horrified by the rampage and offered his prayers to the victims and the people of Virginia. "The president believes that there is a right for people to bear arms, but that all laws must be followed," spokeswoman Dana Perino said

After the shootings, all entrances to the campus were closed, and classes were canceled through Tuesday. The university set up a meeting place for families to reunite with their children. It also made counselors available and planned an assembly for Tuesday at the basketball arena.

After the shooting began, students were told to stay inside away from the windows.

Aimee Kanode, a freshman from Martinsville, said the shooting happened on the fourth floor of West Ambler Johnston dormitory, one floor above her room. Kanode's resident assistant knocked on her door about 8 a.m. to notify students to stay put.

Police said there had been bomb threats on campus over the past two weeks by authorities but said they have 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.

Last August, the opening day of classes was canceled and the campus closed when an escaped jail inmate allegedly killed a hospital guard off campus and fled to the Tech area. A sheriff's deputy involved in the manhunt was killed on a trail just off campus. The accused gunman, William Morva, faces capital murder charges.