One student told the Washington Post that the gunman, said to be about 19 years old, burst into the room and fired about 30 shots in just a minute a half — first blasting a professor in the head, then shooting the students.

Planet Blacksburg — a local, student-run Web site — quoted Ruiqi Zhang, identified as a computer engineering student who said he was on the second floor of Norris.

“A student rushed in and told everybody to get down,” Zhang said. “We put a table against the door and when the gunman tried to shoulder his way in and when he saw that he couldn’t, he put two shots through the door. It was the scariest moment of my life.”

The Web site also quoted Gene Cole, a building worker, as saying the shooter wore a hat and carried an automatic weapon. “He loaded his gun at me,” Cole said. “I ran down the steps to get out of there.”

It was eerily reminiscent of the shocking images from the shootings at Columbine High School in Colorado eight years ago this very week. And something else recalled some of the most shocking images of Sept. 11, 2001: Students jumping from windows to escape.

Virginia Tech sent out a third e-mail at 10:17 a.m. announcing classes were canceled and repeating the warning for everyone to lock their doors and stay away from windows.

By then, the magnitude of this bloody day was becoming increasingly clear.

Grim-faced TV anchors reported the rising death toll: 21, 31, then 33, including the shooter himself, not immediately identified. He put a bullet to his head. Two of the dead were shot at the dorm, the remainder at Norris Hall. Authorities also reported that 26 people were wounded, some seriously.

At 10:53 a.m. — more than two-and-half hours after the terror began — the announcement of the end of the worst mass shooting in U.S. history came in a fourth e-mail from the school.

It read:

“Subject: Second Shooting Reported; Police have one gunman in custody

“In addition to an earlier shooting today in West Ambler Johnston, there has been a multiple shooting with multiple victims in Norris Hall.

“Police and EMS are on the scene.

“Police have one shooter in custody and as part of routine police procedure, they continue to search for a second shooter.

“All people in university buildings are required to stay inside until further notice.