US police went to the Virginia Tech at 0715 (1215 GMT) after reports of "multiple shooting victims" at West Ambler Johnston student hall.
Two hours later, a second call came reporting another shooting at Norris Hall, an engineering building.
All entrances to the 2,600-acre campus were closed and students told to stay indoors away from windows.
Some, but not all, of the dead are believed to be students. One was shot in a dorm, the rest in a classroom, Virginia Tech Police Chief WR Flinchum said.
One of the students said a friend had seen "many bloody bodies".
There were two bomb threats at the campus in the week before the shootings, but police said they were still unsure whether the incidents were linked.
President George W Bush said he was "shocked and saddened" by the killings.
Virginia Tech President Charles W Steger called the shootings "incomprehensible and heinous" and said the university had been hit by "a tragedy of monumental proportions".
With 32 people dead, as well as the gunman, the campus shooting is the worst in US history.
As night fell, shocked students held a candle-light vigil, with many questions about what happened yet to be answered.
Over the course of the night, students paid their respects to those who had died.
Some wrote messages of support on a university sign. Memorial services are expected to take place Tuesday.