BLACKSBURG, Va. — A gunman massacred 32 people at Virginia Tech in the deadliest shooting rampage in modern U.S. history Monday, cutting down his victims in two attacks two hours apart before the university could grasp what was happening and warn students.

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 if 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.

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 "person of interest" in the dorm shooting who knew one of the victims, but he declined to give details.

"I'm not saying there is someone out there, and I'm not saying there is someone who is not," Flinchum said. Ballistics tests would help explain what happened, he said.