The father of a senior at Columbine High School, speaking on condition of anonymity, told the Rocky Mountain News that he had printed out pages from Eric Harris's Internet website more than a year ago and passed them to police because they contained explicit threats to explode bombs and "kill and injure ... as many of you as I can".
The father said he was dismayed when police failed to take action and he complained again a few weeks later. "We continually called back," the father said. "They never called us, ever."
The story fits into a pattern of complaints in which parents expressed alarm at threats and intimidation, by Harris in particular, without any apparent response.
Brooks Brown, an off-again, on-again friend of the killers who survived the shootings because he was warned away at the last minute by Harris, said his family protested after a death threat against him appeared on the Internet site.Isaiah Shoels, the African American student shot dead in the school library, also complained about harassment - although it was not clear if his tormentors were the killers or some other group at the school.
Since Tuesday's carnage, Jefferson County police have consistently denied receiving any warnings. Frank DeAngelis, the principal of Columbine High, said yesterday that he was unaware of Harris's website or of any complaints of specific serious threats.
Making his first public appearance since the shootings, a highly emotional Mr DeAngelis appealed to students and young people everywhere to raise any concerns they have, "so other people don't have to go through what we've been through". Close to tears as he faced the television cameras, Mr DeAngelis seemed psychologically unprepared to face any shortcomings in his administration, merely saying that Columbine High was a "great school" and would continue to be one thanks to the close-knit family feeling among its students and faculty.
Several present and former students, however, have come forward in the past few days saying that all members of the so-called Trenchcoat Mafia, the introspective clique to which Harris and Klebold belonged, knew how to make pipe bombs. One claimed that the police were aware before the attack that these were being manufactured in the two boys' homes with materials readily available from hardware stores - carbon monoxide canisters, fuses, glass and nails. Gunpowder is highly restricted in Colorado, but is freely available from powerful fireworks on sale across the state line in Wyoming.
Neighbours of Harris have said they heard the sounds of bottles being smashed at his home last weekend, but never suspected they were to be used as shrapnel stuck on to the pair's home-made explosives. "We thought it was a school project or something," one neighbour said.
It is not known where the student's parents or older brother were at the time.
More details also emerged yesterday of the weaponry used in the attack, which included a modified version of a notorious semi-automatic handgun, the TEC-9, much used by street gangs and featured in the movie Robocop. The pair also carried a 9mm semi-automatic carbine, a pump-action shotgun and a sawn-off double-barrelled hunting gun.
According to local media reports, the two semi- automatics were purchased legally from a licensed Colorado gun-dealer, although it seems that Harris and Klebold acquired them through an intermediary because they were too young to buy the weapons themselves.
According to one teenager in Littleton, arranging to buy such weaponry is not difficult. "I have a friend of a friend who could get me a 50-calibre rifle for $200, or a fully automatic AR15 with bullets with exploding tips - which is totally illegal - for three or four hundred," said the teenager, Joe Costello, who attended a similar Littleton high school for a year and a half before ducking out because of teasing and bullying from the "jocks" - the same group that Harris and Klebold complained about.
Interviews with similar teenagers, who are marginalised in the conservative suburban atmosphere of Littleton, suggested that bullying by jocks is a serious problem. Mr Costello said he had been pushed and beaten repeatedly and had rocks thrown at him, but the school authorities appeared uninterested in protecting him or punishing the well turned out, sporty jocks.