Two teenage boys have been convicted of conspiracy to murder at their North Yorkshire school for plotting a Columbine-inspired shooting at their school and planning to build a Manchester Arena nail bomb replica.
The 14-year-olds planned to kill pupils and teachers in a re-enactment of the 1999 Columbine High Schoolmassacre, Leeds Crown Court wastold.
They also downloaded a book called Anarchists Cookbook Version 2000 - a guide that provides instructions on the manufacture of bombs, including pipe bombs and nail grenades, and explosives, including napalm and nitroglycerin.
Prosecutors said ultimately their plan was to make a nail bomb like the one detonated at the Ariana Grande concert.
Both now 15, they sat motionless alongside their tearful mothers as the verdicts were read to them on Thursday.
The older boy, wearing a shirt, was also convicted of unlawful wounding, but cleared of a count of aggravated burglary.
During the three-week trial, prosecutors claimed that the pair "hero-worshipped" Eric Harris and Dylan Klebold, the teenagers responsible for murdering 13 people at Columbine High School, Colorado, in 1999.
The judge, Mrs Justice Cheema-Grubb, told the pair they will be sentenced at a later date when she has considered reports about them both.
She told the jury: "Nobody will be in any doubt as to the gravity of their conduct and the plans they have made."
She said it was an "unusual case" but told the jury the "welfare of young people" was the primary concern of the sentencing system.
The teenagerswent on trial at the beginning of the month charged with conspiracy to murder and other offences relating to a planned attack at their school in the North Yorkshire market town of Northallerton.
Paul Greaney QC had included, in his original opening, but chose not to tell the jury: "Such bombs are designed for one purpose, not to damage property but rather to kill and maim people. To that end, an explosive device is packed with metal shrapnel so that when the explosion occurs, the shrapnel is propelled out at speed, and into the bodies of people nearby.
"Such a device was used, as you will all recall, to kill 22 people and maim hundreds of others at the Ariana Grande concert at Manchester Arena on May 22, 2017."
Mr Greaney didtella jury however that the boys hero-worshipped Eric Harris and Dylan Klebold - the teenagers who killed 12 students and a teacher at Columbine High, in Colorado, before shooting themselves.
He said: "Eighteen years after the ColumbineMassacreand nearly 4,500 miles away, two young teenagers in North Yorkshire became fascinated with Eric Harris and Dylan Klebold.
"Those two teenagers researched and discussed those killers and their interest in them turned to hero-worship. It was against that background that they plotted their own attack upon the school they attended.
"In that attack, they intended to shoot and kill other pupils and teachers against whom they held a grievance.
"They also, like their heroes, intended to deploy explosives and researched bombing-making techniques to that end."
Mr Greaney said: "They intended a re-enactment of the Columbine High SchoolMassacrealthough fortunately, in the result, they were stopped before their plans were put into action."
Both boysdenied a joint charge of conspiracy to murder relating to a period between December 31 2016 and October 29 2017.
Neither of the convicted boys nor the school can be named.
Mr Greaney told the jury that the "hideout" of one of the boys - described as the apparent leader of the pair - was found in an abandoned shack in the village of Catterick Garrison and contained "various items, including materials that were capable of being used in bomb-making".
He said this was evidence "that this plan was real, not fantasy".
"(This boy) asserts that there is an innocent explanation for his possession of the items, which include petrol and a bag of screws, but we will invite you to conclude that his explanation is untrue," he said.
The prosecutor said the defendants downloaded, within two minutes of each other, a bomb-making manual from the internet.
And he told the jury that one of the boys, the apparent leader, kept a diary with "significant and disturbing content".
Mr Greaney said: "Even the diary that has been recovered demonstrates that (the boy's) murderous intentions were real."
He also told jurors that this boy had carved his name into his girlfriend's back with a knife. Healso carved her name on his arm – but spelt it wrong.
The prosecutor told the jury what happened in the ColumbineMassacreand said the defendants would "emulate" the perpetrators' habit of wearing trenchcoats.
Mr Greaney told the jury that the alleged leader of the pair was excluded from school in April 2017 after staff found a fake Instagram account being used to post offensive images and comments about teachers.
He said this boy continued to search the internet for material about the ColumbineMassacreand the other defendant showed an interest in bomb-making techniques, saving screenshots of specific pages of the Anarchy Cookbook dealing with nail bombs and making home-made gunpowder.
Mr Greaney said the pair had a conversation on an instant messaging platform in May 2017 which went:
"Boy 1: 'I can't be bothered anymore.'
"Boy 2 (the alleged leader): 'Why not take some others out as well?'
"Boy 1: 'What do you mean?'
"Boy 2: 'If you're gonna kill yourself, shoot up the school."'
