In videos made before their assault on Columbine High School, the two teenage gunmen who killed 12 students and a teacher said they wanted to "kill 250" and "kickstart a revolution".

Twelve students and one teacher were killed when Eric Harris and Dylan Klebold went on a shooting rampage at Columbine High School in Littleton, Colorado, on 20 April, before taking their own lives.

One month after US police first revealed the existence of the tapes, Time magazine reporters have described the evidence.

Harris and Klebold made at least five tapes of the events leading up to the school massacre. The last was recorded less than an hour before the shootings.

Before embarking on their rampage, the teenagers declared that they would inspire a cult following of youth outcasts at schools across the United States, the magazine says.

They were determined to be seen as originals.

'No copycats'

"Do not think we're trying to copy anyone," Eric Harris says, referring to earlier school shootings in Oregon and Kentucky.

They had the idea long ago, "before the first one ever happened," he claims.

Their hatred was directed against "niggers, spics, Jews, gays", but also whites who did not side with them.

Dylan Klebold foresees the planned assault as the most "nerve-racking 15 minutes of my life, after the bombs are set and we're waiting to charge through the school.

"Seconds will be like hours. I can't wait. I'll be shaking like a leaf."

Tapes withheld

"Directors will be fighting over this story," says Dylan Klebold on one of the tapes.

Jefferson County deputy district attorney Steve Jensen, who revealed the existence of the tapes in November, said: "It's obvious that these guys wanted to become cult heroes of some kind."

Mr Jensen said the police had not previously revealed the existence of the tapes because they were made with that intention.

"Dissemination of this material might allow Klebold and Harris to accomplish their goal, and we don't want them to appear to achieve that kind of status," Mr Jensen said.

Thought for the parents

Throughout the tapes the killers show hardly any remorse, although they are clearly aware that what they are about to do will ruin their parents' lives.

"Good wombs hath borne bad sons," Eric Harris quotes from Shakespeare's The Tempest.

They recall how they were picked on and bullied at school, how they felt excluded by their own families.

Except for his parents, Dylan Klebold says, his family treated him like an outcast.

"You made me what I am. You added to the rage.

"Being shy didn't help. I'm going to kill you all."

They defend the friends who bought the guns for them. These friends knew nothing of their intentions, Harris and Klebold say

If they had not been able to get hold of the guns Eric Harris says, "we would have found something else".