Monday's massacre was the deadliest shooting rampage in modern US history, with the unidentified gunmen cutting down his victims in two attacks before turning the gun on himself and taking his own life.

Liviu Librescu, 76, an engineering science and mathematics lecturer, tried to stop the gunman from entering his classroom by blocking the door before he was fatally shot, his son said Tuesday from Tel Aviv, Israel.

"My father blocked the doorway with his body and asked the students to flee," said Joe Librescu. "Students started opening windows and jumping out."

Librescu immigrated to Israel from Romania in 1978 and then moved to Virginia in 1985 for his sabbatical, but had stayed since then, said Joe Librescu, who himself studied at the school from 1989 to 1994.

Another foreign professor was also killed. Indian-born G.V. Loganathan, 51, a lecturer at the Department of Civil and Environmental Engineering, was felled by the gunman, his brother GV Palanivel told the NDTV news channel from the southern Indian state of Tamil Nadu.

Palanivel said he was informed by Loganathan's wife, who had identified the body.

"We all feel like we have had an electric shock, we do not know what to do," Palanivel said. "He has been a driving force for all of us, the guiding force."

Loganathan, who was born in the southern Indian city of Chennai, had been at Virginia Tech since 1982.