As a child, he had survived the Holocaust. As an adult, he had survived persecution for defying Romania’s brutal communist regime during the Cold War. At last, with their children grown, he and his wife, Marlena, seemed to have found a safe haven on a quiet university campus in rural Virginia.

But on Monday, trouble found him once more. With bursts of gunfire rattling through the second floor of Norris Hall, Librescu, 76, closed his classroom door and urged his students to escape out the windows, recalled senior Caroline Merrey of Baltimore, the third student to jump.

As they fled, Librescu held the door shut with his body as the gunman, Cho Seung-Hui, tried to force his way in.

Moments after the last student leapt to safety, Cho apparently succeeded in forcing the door open and shot Librescu to death.

“My father has showed a sense of his courage in standing up for what he believed since long ago,” said Joe Librescu, the professor’s son.

“Just one candle can light up a room filled with darkness. Professor Librescu has lit the entire world with hope, reminding us that heroes can still exist even in our dark times,” Evan Goldenthal of Toronto wrote on a Facebook.com page of tributes to the professor.

But it was not the only story of bravery and determination in the face of mortal danger. Elsewhere in the building, students fought off attempts by the gunman to force open the doors to their classrooms. In one case, Cho had shot as many as a dozen students in a German language class, then departed in search of new targets. Two students held the door shut when the gunman returned; he reportedly fired several rounds into the door in frustration.

Derek O’Dell, a 20-year-old sophomore majoring in biological sciences, said the gunman entered his classroom and opened fire without saying a word. O’Dell said most of the students in the class were hit. A bullet struck him in the right arm.

Cho left the room, and O’Dell and another student slammed the door and held it shut with their feet. Minutes later, Cho reportedly returned and tried to push his way back into the classroom.

Another student who kept Cho at bay was Zach Petkewicz. “I was completely scared out of my mind initially and then realised, you’ve got to do something. And so I said, ‘We need to barricade this door.’ Me and two others got up, threw a couple of tables in front of it, and had to physically hold it there. ... He came to our door, tried the handle, couldn’t get in,” Petkewicz told CNN.

“He tried to force his way in, got the door to open up about six inches, and then we just lunged at it and closed it back up. And that’s when he backed up and shot twice into the middle of the door.”

Minutes later, when police reached the second floor of Norris Hall, they found Cho dead, apparently having killed himself.

In the case of Liviu Librescu, violent death came with a special irony: it arrived when he seemed to have found tranquillity after a life of danger and struggle. He had become a popular professor with an international reputation in aeronautical engineering.

In Israel, Monday was Holocaust Remembrance Day.

-Richard T Cooper & Valerie Reitman