BLACKSBURG, Va. — When the shooting was over Erin Sheehan raised her head slowly and looked around the room. The horrific scene around her told her that her crude survival instincts had saved her life. When the gunman burst into her German class in Norris Hall and started methodically shooting students, she hit the floor and played dead.

“He seemed very thorough about it, getting almost everyone down. I was trying to act dead,” said Ms. Sheehan. “He left for about 30 seconds, came back in, did almost exactly the same thing.”

Three more times the attacker returned as the students fought desperately to keep the door shut on him. Frustrated, he pumped his ammunition into the wood.

When it was over, Ms. Sheehan was the only one out of 20 or so students in the room in Norris Hall who were unhurt. “Everyone was else was unconscious, either dead or wounded seriously,” she said. Others survived by leaping out of windows, cowering in cupboards, or running for their lives.

Alec Calhoun, 20, said he did not hesitate to hurl himself to safety after hearing gunshots next door. “It took us a few seconds to realize what it was. At first, it sounded like an enormous hammer, a kind of explosion. Then we heard the screams and realized that something was wrong.

“I knocked over desks and pulled screen windows and jumped from the second floor,” Mr. Calhoun said. “I could see people in front of me land and hurt their ankles and legs.

“I aimed for a bush thinking it would help break my fall, and I landed on my back,” he said. “The two people directly behind me jumping out were shot; they’re both in the hospital.” One required surgery to remove a bullet and is intensive care, he said. Mr. Calhoun ran across a lawn and hid between two buildings until the police ushered them away.

“I somehow expect I’ll wake up and think it was all some kind of dream, some terrible nightmare.”

His classmate Josh Wargo, who also jumped, said: “We could hear people screaming, ‘Oh my God’ from next door. Everyone started to panic and jumping out of the window. As soon as we heard the shots, people started calling 911. When I landed, I was in a daze, standing outside of the building. Then I heard shots going through glass, that’s when it hit me that I had to get out of there,” he said.

He said he received the university’s warning e-mails but thought they were a prank or “nothing serious.”

Pam Tickle, a housekeeper at Norris Hall, described just another easygoing morning when shortly after 9:30 a.m. she heard gunfire coming from the corridor. “We weren’t quite sure what happened at first,” she said.

Mrs. Tickle and several students rushed to a student lounge on the second floor, locked the door, and waited almost two hours for police officers to evacuate them.

“We peeked out the door one time but more shots were fired,” Mrs. Tickle told a student Web site, Planet Blacksburg. “We stayed in there not knowing what happened. When we heard police out in the hallway after 11, we let them in.”

Mrs. Tickle only felt safe when a little after 10 a.m., she heard an announcer on the police radio who said, “Shooter’s down!” “I thank God because he was watching me today,” she said.

Tiffany Ottey recalled the chilling sense of dread as she huddled with fellow students in a locked room while the gunman stalked the corridors below, firing 50 rounds by her count.

“I guess everybody was like freaking out, hysterical,” she said. “Who knows if the shooter was going to come up to the next floor?”