The young gunmen moved calmly through the school library, giggling as they shot point blank at students cowering under their desks.
Stunned teenagers at Littleton's Columbine High School described yesterday's attack as a horror movie come to life, pointing to a group of school outcasts known as the "Trenchcoat Mafia" as being likely suspects in a rampage which cost as many as 25 lives.
Two heavily-armed gunmen, dressed in black trench coats and ski masks, blasted their way through the large, suburban high school as students were going to class or headed for lunch.
When it was over, the two gunmen lay dead in the library of what police reported to be self-inflicted wounds.
Police said that initial sweeps of the building indicated that 23 other students, teachers and school employees may have died in the bloody assault.
One female student, her arms spattered with the blood of her fellow students, sobbed as she told KMGH television, "He was shooting people right in front of me. He was shooting people of colour and people who play sports.
"He put the gun right in my face and started laughing and said it was because people were mean to him last year."
Many witnesses said the gunmen appeared to have two particular targets - minority students, and popular athletes.
A first-year student named Joshua Lapp said he was in the school library when the gunmen approached. He ducked beneath his desk along with others in the room when the shooters entered.
"They came in started shooting people underneath the desk. About half an hour shooting, they decided to walk out," he told a reporter.
"They were going around, they were laughing about it," he said. "They'd shoot somebody, they'd laugh, they'd giggle . . . you'd hear a shot go off, you'd hear somebody yell and scream, another shot go off and they'd yell and scream, another shot and there would be silence . . ."
Lapp was one of a number of students who said the gunmen's all-black outfits resembled the black trenchcoats sported by the "Trenchcoat Mafia", a group of teenagers who favoured dark clothing and "gothic"-style rock music.
"They were known as the Trenchcoat Mafia at our school and they got ridiculed a little bit," Lapp said. "We called them the Trenchcoat Mafia because they wore black trenchcoats every day to school. Everywhere, anywhere, any day, no matter how hot it was they wore a black trenchcoat." He added that the social tensions between the school athletes, or "jocks", and the "Trenchcoat Mafia" may have been one factor behind the attack.
Other students at the school described equally chilling scenes as explosions rocked part of the school and bullets went ricocheting off lockers.
"I heard people pray for their husbands, their children, you name it," said senior Nick Claus, who took refuge with several other students and school workers in a bathroom.
"They just started shooting. Anybody who was walking, talking they just shot. That was the sick part about it . . . all I saw was big black trenchcoats and guns, man, and bombs."