Two 14-year-old boys planned to re-enact the Columbine High School massacre by killing pupils and teachers at their school, a jury has been told.
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The pair, both now 15, hero-worshipped Eric Harris and Dylan Klebold - the teenagers who killed 12 students and a teacher in Colorado in 1999 - prosecutors told Leeds Crown Court.
The court heard how the boys emulated the Columbine killers' habit of wearing trench coats and the older of the two - said to be the leader - "idolised" Harris.
Paul Greaney QC, prosecuting, told a jury on Thursday the pair were planning an attack at their school in the North Yorkshire market town of Northallerton and shared a list of people they wanted dead.
Mr Greaney said: "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 School Massacre although fortunately, in the result, they were stopped before their plans were put into action."
The defendants - one wearing school uniform - each sat with one of their parents as they listened to the case opening.
The prosecutor described how the elder boy had started a relationship with a girl in June last year and, at one point, had carved his name into her lower back.
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He said the girl's father kept seven shotguns in a locked cabinet and that the boy regularly asked about them and "sought access to them as part of the plan to attack the school".
After the girl's parents banned the pair from seeing each other, the boy went to her house "dressed like Eric Harris and was wearing a t-shirt on which he had written a slogan in pen that was a threat ... to her parents," he said.
Mr Greaney said the boy fled carrying a large knife which was later found with the word 'Love' written on the blade.
A diary was later found in which the boy had written: "Her parents need to die. I hate them so f****** much it's insane".
He also wrote: "I'll run away to Catterick and lay low for a while then we murder her parents and we'll stay at her house for a while and get all of her dad's guns and I'll make some explosives then we'll find a way back to Northallerton and we'll begin our assault on that f****** school."
Mr Greaney said that this was "no teenage fantasy; it was real".
The prosecutor said that at one point the younger boy made confessions to school staff and police but he told the jury that "you may conclude that the police in North Yorkshireresponded inadequately to the threat these two defendants presented, although a month later a specialist anti-terrorism team who became responsible for the investigation, responded more appropriately, and robustly".
Mr Greaney said a "hideout" in the village of Catterick Garrison was found which contained "various items, including materials that were capable of being used in bomb-making".
He told the jury of five men and seven women that "in very simple terms, (the younger boy) suggests that (the older boy) was serious about the mass killing, whereas he was not. And (the older boy) suggests that no-one was serious about any of it".
Both deny a conspiracy to murder and a range of alternative charges.
The older boy also denies unlawfully wounding his girlfriend and the aggravated burglary of her parents' house.
The trial, which continues on Friday, is expected to last four weeks.