The five-minute tape gave the first real glimpses of terror inside Columbine High School as Eric Harris, 18, and Dylan Klebold, 17, calmly strode through the halls murdering 12 schoolmates and a teacher.

Much of the tape was unintelligible, but when it was audible, it was chilling. ``I do not know them,'' said a teacher, her voice rising breathlessly and quickly to a high pitch. ``He turned the gun straight at him...and I think he got hit in the right shoulder...Oh, God! Oh, God!'' The police said the teacher escaped injury.

The police released the tape as some 150 investigators met to share information on their probe for possible accomplices of Harris and Klebold, who killed 13 others and then shot themselves in the face.

Investigators are also reviewing a week's worth of videotapes from schoolsurveillance cameras that might give clues of accomplices and how the duo managed to get so many explosives into the school.

The investigation sharply broadened on Thursday when investigators found in the school two 20-pound tanks rigged together to act as a single powerful bomb that could have caused massive damage. Clear signs have also been found that could have indicated that the deadliest attack in an American school was on its way.

Harris and Klebold had made a tape in their video production class showing them shooting students as they walked down the school corridors, students now recall.

Fellow student Eric Veik, who helped make the video, told The Denver Post that the pair recently joked that ``It's time to plan the senior prank for the class of '99, and they made comments that Hitler's birthday was coming up.''

Authorities had evidence a year ago that Eric Harris was contemplating mass murder, but did nothing, said Randall Brown, who saved printouts from Harris's website to support hisclaims. Brown said Harris had threatened Brooks, his son, and had broken his windshield. When Brown complained to authorities, Harris posted this Internet message: ``If anybody wants to kill someone, why not Brooks Brown?''

``I will rig up explosives all over town and detonate each one of them...after I mow down a whole...area full of you,'' said one the printouts.About the same time that Brown filed a complaint with the Sheriff, Harris and Klebold were finishing a correction programme after breaking into a car. As part of the programme, they had to promise that they would not possess weapons. In fact, they were building their first pipe bombs at the time, according to Harris's March Web page.

The printout also offered a stark forecast: ``I am the law, if you don't like, you die.'' In his America Online user profile which has since been dismantled, Harris wrote: ``Shut up and shoot it'' and ``Quit whining, it's just a flesh wound...Kill 'em AALLL!''

-- Agence France Presse