31 people have been killed and another 10 injured after a gunman went on the rampage at a US college campus.
The dead are believed to be mostly students at Virginia Tech in Blacksburg, a state university known for its demanding science and engineering curriculum.
One student was killed in a dormitory while others were shot in a classroom, said Virginia Tech police chief WR Flinchum.
The gunman – who was said by witnesses to have been carrying a large amount of ammunition – was also killed although police have not confirmed if he turned a gun on himself or was shot by marksmen.
President George W Bush said he is "horrified" at the news.
College president Charles Steger added: "Today the university was struck with a tragedy that we consider of monumental proportions. The university is shocked and indeed horrified."
The first reports of an incident came at around 7.15am (1115 GMT) in West Ambler Johnston Hall, a dormitory housing some 900 students. Most of the shootings occurred at another campus building, Norris Hall.
Student Matt Maroney said fellow students threw desks at a door and a teacher was shot in the arm.
He added: "He had an ungodly amount of ammo on him. He was just dressed in a vest filled with clips and started firing away at classrooms.
An injured person is carried out of Norris Hall. Police say the shooter went to Norris after firing shots at a dorm.
Area law enforcement officers take their positions on Clay Street on the Virginia Tech campus.
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Two people were killed at a dormitory about 7:15 a.m., while another 30 people were killed about two hours later at Norris Hall — the engineering science and mechanics building — university officials said.
University police Chief Wendell Flinchum said police were still investigating whether the two incidents are related. Investigators are not ruling out a second shooter, Flinchum said.
The death toll at Norris Hall makes the incident the deadliest mass shooting in U.S. history.
The gunman at Norris Hall, who police say took his own life, was not carrying identification and has not been identified.
Freshman Erin Sheehan told the university newspaper she was in German class at Norris when the gunman peeked in twice "like he was looking for someone" and then started shooting.
The students tried to blockade the door, but the shooter — dressed in "a Boy Scout-type outfit" — made it inside.
The remaining students, about 20 of them, were dead or injured, she told the newspaper.
"Norris Hall is a tragic and a sorrowful crime scene, and we are in the process of identifying victims," university President Charles Steger said.
We send our deepest love, and care to the familey’s of the dead..