With every shell casing and piece of bomb shrapnel now being counted and catalogued, police in Colorado are expanding their investigation to determine whether the two teenage shooting suspects had help.
Two additional bombs weighing 35 pounds were found yesterday in the school's kitchen. "There was a large number of (explosive) devices and it wasn't done in a couple of hours," said District Attorney Mr Dave Thomas. "It is possible other people were involved in constructing those devices."
Investigators said they were looking into the possibility that the gunmen also intended to destroy the building.
Eric Harris and Dylan Klebold shot themselves during a killing rampage at Columbine High School in Littleton, Colorado that left 15 dead and 23 injured. Police are interviewing classmates of the two, and painstakingly going through their computers and information obtained from the Internet company used by the boys.
More than 30 bombs were also found on the school grounds, in Harris's black BMW, and at his home. Some had sophisticated timing devices. What is disturbing to many is the length of time and the preparation that were clearly involved in planning the massacre and building the bombs. How could no one - parents, classmates, school authorities - have noticed?
Children playing on the street where Harris lived reported that over the weekend they listened as sounds of breaking glass and machinery could be heard from his garage. They also said that Dylan Klebold's car was parked there.
Both boys came from respected families in the well-off community. Harris's father was a retired Air Force pilot. Neither set of parents was aware that the boys were assembling an arsenal in the garage. The explosives ranged from pipe-bomb devices, filled with nails and paper clips as shrapnel, to volatile propane devices.
As experts insisted that violent youths always give warning signs, school authorities at Columbine stayed silent. Classmates of the two said that, in addition to wearing black trench-coats, they often spoke German, shouted "Heil Hitler!", discussed bomb-making, and were obsessed with combat.
Denee Taylor, a senior at the school, said she knew several members of the group. Without disclosing a name, she mentioned taking a class with one of its leaders.
"He really liked weapons," she told the Los Angeles Times.
"In economics class, we had to create a company and sell its products. I invented a comic book company. He created a weapons manufacturing plant."
Predictably, vigorous discussion on the airwaves, in newspapers and on talk radio began this week as sociologists, criminologists, and adolescent psychologists debated the root cause and triggers for America's increasing youth violence.
"We are obsessed with violence as a people," said Mr Richard Slotkin, a history professor at Wesleyan University and author of The Myth of the Frontier in 20th Century America.
"We're shocked by images from Littleton, but bombing Belgrade is OK. There are serious moral and political issues here and yet this country hasn't begun to sort them out," he told the Los Angeles Times.
The debate over gun control was, of course, stirred by the shooting, and a cacophony of voices rose on that score.
Texas Governor Mr George Bush, a candidate for president, said that love, not gun control, was the best preventative measure.
"I wish I knew the law that would make people love one another," he told reporters.
Reuters adds:
The two teenagers suspected of killing 12 fellow students and a teacher and then taking their own lives left a note before going on their shooting rampage, CNN reported yesterday.
Quoting two unnamed sources, CNN said there was a note in which the suspects, Eric Harris (18) and Dylan Klebold (17), said, "Don't blame anyone else for our actions. This is the way we want to go out."