Thirty-three people died on Monday in a massacre at a US university campus in the bloodiest school shooting in the country's history.
The exact details of what happened remain sketchy, but here is a timeline of events released so far:
7:15 am: A 911 call is made to police informing them of a shooting at the West Ambler Johnston Hall, one of the campus dormitories. A man and woman are found shot dead.
7:30am: Two wounded people are taken to Montgomery Regional Hospital, the nearest hospital to the campus.
Investigators follow up leads in relation to "person of interest" in relation to double homicides.
8:00 am: Classes begin for most of the 9,000 students who live on campus and the thousands more who come from outside.
Police evacuate the dormitory and begin to question witnesses. Thinking that the shooter has left the campus, they decide with the university's agreement to treat it as an isolated incident.
8:25 am: Virginia Tech school officials assemble to begin assessing the situation at the residence hall and to determine a means of notifying students.
9:26 am: Students are informed of the shooting in the dormitory by an email advising them to be cautious and to contact police if they see anything suspicious.
9:45 am: University police receive an emergency call of a shooting in the engineering building Norris Hall call police.
The unidentified gunman advances class by class killing 30 people before turning the gun on himself. According to witnesses he was Asian and wore a black jacket.
About 15 wounded, some of them seriously, are taken to hospitals.
Police rush to the building to find the front doors barricaded with chains from the inside. Police break down doors and hear gunshots.
They follow the succession of gunshots to the second floor. Just as they reach the second floor, the gunshots stop and police discover the gunman, who had taken his own life.
9:55 am: "A gunman is loose on campus. Stay in buildings until further notice. Stay away from all windows," says a second email. Loudspeakers broadcast a similar message.
10:16 am: A third email announces that all classes have been canceled and urges students "to remain where they are, lock their doors and stay away from windows."
10:52 am: A fourth email warns of "a multiple shooting with multiple victims" in Norris Hall, saying the gunman has been arrested and that police are hunting for a possible second shooter. The entrances to the campus are locked.
In fact the gunman is dead, but police are not sure if they have the shooter. Authorities remain uncertain whether the two incidents are linked and cannot rule out that the dormitory shooter is still on the loose and could reappear.
12:15 am: University president Charles Steiger and campus police chief Wendell Flinchum tell a press conference that more than 20 people have been killed.
During the afternoon the toll rises to at least 33 dead, including the gunman.