AUTHORITIES SLOWLY SECURE TORN CAMPUS.

Byline: Sam Howe Verhovek The New York Times

As parents waited in agony nearby and police squads searched for explosive booby traps inside, authorities carefully made their way through Columbine High School on Wednesday where they found the bodies at least 15 people killed by gunshots or homemade pipe bombs in a massacre Tuesday.

Among the dead were the two members of the senior class who are believed to have unleashed the carnage before turning their guns on themselves. They were found shot in the head.

Twelve of the dead, including both suspects, were found in the school's library, said the Jefferson County sheriff, John Stone, who added that there were so many weapons and explosive devices - including 30 bombs, a semiautomatic rifle and pistol and two shotguns - that investigators were still unsure how they got it all inside the school. They may have hidden it during several trips or they may have had help, Stone said.

David J. Thomas, the district attorney, at a press conference at the school Wednesday afternoon, said there are two or three active separate investigations of a Web site connected to the suspects in the case.

``There has been a Web site for some time,'' he said.

Thomas said that investigators are looking at eight to 10 people who might have knowledge of the case.

``I think there is evidence to suggest that other people were at least aware of what was going on. There were a lot of devices. They took a long time to construct and a lot of people were familiar with the Web site.

Stone said a computer had been seized at a suspect's house, and they were tracing the e-mails.

But an even more unfathomable set of questions surrounded the motivations of the two suspects, 18-year-old Eric David Harris and Dylan Bennett Klebold, 17, who were described by many students Wednesday as members of a self-styled group of loners and outcasts who called themselves the ``Trenchcoat Mafia'' after the long black coats they wore and shared a fascination with violent video games and a antipathy toward the more popular students who they referred to as ``jocks.''

Both Harris and Klebold were arrested last year for breaking into a car, and parents of another student at the school said that they had complained to authorities last year about death threats made by Harris against their son. Nonetheless, school authorities and many students insisted Wednesday that they never seriously considered either young man to be inclined toward the horrific violence let loose here Tuesday.

The incident set off a national bout of soul-searching and debates over whether the killings were spurred by easy access to guns or by the violent images on television and in video games to which America's children are routinely exposed.

President Clinton said in Washington that ``all of us are struggling to understand exactly what happened and why.''

The shootings also had immediate political reverberations as well: In at least three states, including Colorado, sponsors of legislation expanding the rights to carry guns withdrew those measures Wednesday.

Danger fear

The authorities were still so concerned about the possibility of more danger that all of the bodies were not removed from the school until Wednesday evening. Some were so unrecognizable that parents were asked to bring dental records of their missing children to the school.

The death toll, which represents the largest school massacre in the country's history, was a downward revision from the possible 25 deaths that the authorities had said on Tuesday. But it was unclear whether it would rise again as the search inside the school continued.

Eleven of the dead are male, including at least one teacher and one black student whom the killers had shot in the head.

Sixteen people are still hospitalized, 11 of them in serious or critical condition, according to a spokesman for the sheriff's office.

All day long, under sunny skies that turned slate grey with an approaching storm Wednesday afternoon, students gathered near the high school for any news about friends still officially listed as missing. Many were crying or clutching flowers that they brought to a makeshift memorial.

``I can't even imagine walking into that school right now,'' said 17-year-old Dara Ferguson, a junior, who had three friends whom she feared were dead. ``I don't think I ever want to set foot in there again.''

Officials with the Jefferson County School District said that the building, with hundreds of bullet holes and several inches of water that came from sprinklers that went off after the bombs did, would remain closed for the rest of the school year.

Bills postponed

In Alabama and Florida, the school shooting prompted lawmakers to postpone consideration of bills that would prohibit cities and counties from suing gun makers for the cost of gun violence. The bills, similar to others passed around the country, were introduced at the behest of the National Rifle Association to protect the firearms industry from liability suits.

But at least some politicians said that the violence might have been averted if someone else had been armed at the school.

``Had there been someone who was armed, in this particular situation, in my opinion, it may have stabilized,'' said Minnesota Gov. Jesse Ventura, who supports loosening restrictions on concealed handguns. ``I believe it supports conceal and carry because of the fact that what happens when a group of unarmed individuals are confronted with people with weapons like this, you have no defense.''

And Charlton Heston, president of the National Rifle Association, said the incident showed that there should be armed guards in the nation's schools.

``If there had been even one armed guard in the school, he could have saved a lot of lives and perhaps ended the whole thing instantly,'' he said in Los Angeles on Wednesday. There was, in fact, an armed guard at the school and he exchanged fire with one of the suspects.

GETTING HELP

Anyone concerned that a child or fellow student may turn violent should contact that youth's parents, teachers, or officials at his or her school, including counselors, administrators or nurses, say officials at the Los Angeles Unified School District.

Other places to seek help include:

To report a potentially violent situation or crime, call (800) 78-CRIME, a national, anonymous crime-reporting line the LAUSD uses.

Los Angeles County Mental Health Services [phone]

California Youth Crisis Hot Line [phone]

National School Safety Center, Westlake Village [phone].

Boystown National Hot Line [phone]

Suicide Prevention Center [phone]

CAPTION(S):

2 photos, box

PHOTO (1 -- color) Columbine High School students try to console each other Wednesday near the car of one of the victims.

Michael S. Green/Associated Press

(2) Students comfort one another during a prayer service at Light of the World Catholic Parish in Littleton.

Craig F. Walker/The Denver Post

Box: Getting help (see text)