Virginia in Day of Mourning

Virginia was today observing a day of mourning for the 32 victims of the Virginia Tech killer as universities and schools around the country struggled with a series of copycat threats.

Also today, in Denver, Colorado, Columbine High School was closed, as it has been on every April 20 since the 1999 shootings in which students Eric Harris and Dylan Klebold murdered 12 classmates and a teacher before killing themselves.

The day of mourning was declared by Virginia's governor, Timothy Kaine, who called for a moment of silence at noon in memory of those shot dead by 23-year-old student Cho Seung-hui.

Mr Kaine also announced the appointment of an independent panel, including the former homeland security secretary Tom Ridge to look into how authorities handled the tragedy.

Asked today if the attacks had been preventable, Mr Ridge said his "preliminary judgment would be probably not", but that he hoped to be able to find ways to reduce such risks in the future.

Churches around the country, including the national cathedral in Washington DC, have scheduled vigils and special prayer services.

"We want the world to know and celebrate our children's lives, and we believe that's the central element that brings hope in the midst of great tragedy," said Peter Read, whose 19-year-old daughter, Mary Karen, was killed.

He joined other parents in attacking NBC for deciding to broadcast rambling, hate-filled videos made by Cho as part of a package of films, still photographs and printed matter.

After killing two students, Cho paused for two hours, posting the package to NBC in New York, before killing 30 other people and then himself.

The head of Virginia state police, Steve Flaherty, told a press conference yesterday that he was "rather disappointed" at NBC's decision. The television station defended its actions, saying virtually every other news organisation in the world had also used the material.

The massive publicity surrounding the worst mass shooting in US history has sparked a spate of copycat threats, one of which saw several schools in California cancel classes and evacuate students.

Police in Yuba City, just north of Sacramento, said they were told a man had threatened to carry out an attack that would "make the incident at Virginia Tech look mild by comparison". A 28-year-old man later handed himself in to police.

Around a dozen similar phone and internet threats were made nationwide, the bulk of them referring to Monday's shooting.

Today also saw a series of funerals of some of Cho's victims, among them Liviu Librescu, a 76-year-old aeronautics lecturer who was killed while barricading a door to try and keep the killer away from his students.

The Holocaust survivor was buried in Israel, having been posthumously awarded the highest award for valour by his native Romania.

After Cho was identified as the killer, students and fellow teachers spoke of him being painfully shy and withdrawn, almost never engaging others in conversation. It later emerged that in 2005 he had been accused of stalking two women and was admitted to a mental health hospital, where he was evaluated as a possible suicide risk.

"In virtually every regard, Cho is prototypical of mass killers that I've studied in the past 25 years," James Alan Fox, a professor of criminal justice at Northeastern University in Boston, Massachusetts, told the Associated Press.

"That doesn't mean, however, that one could have predicted his rampage."

Cho's parents, who run a dry cleaning business in Centreville, Virginia, have yet to speak publicly.

The South Korean ambassador to the US, Lee Tae-sik, said today that they were receiving US government protection and "move from place to place every day".