An army cadet who praised Adolf Hitler constructed a potential bomb after researching instructions online, a court has heard.
The 16-year-old, who cannot be named for legal reasons, allegedly told fellow students he was going to kill as many people as possible on a rampage.
The court heard that the boy had been radicalised through “progressively dark” online searches.
Opening the case, Paul Greaney QC said: “Like many young teenagers, the defendant had strong opinions and an intense interest in the Internet.
"However, as he became older, both his opinions and his use of the Internet became increasingly disturbing, indeed menacing.
"Not only did he research extremism, but he also began to access videos and information about murder, torture and mutilation.”
Prosecutors said the teen researched bomb making before creating a device by strapping together two C02 canisters and filling one with shrapnel.
If gunpowder was added to it, it could have been a 'viable C02 bomb', Leeds Crown Court was told.
The boy was referred to the government’s Prevent programme when he was 13, after telling a police officer he had praised Hitler and researched how to make a bomb.
He met an intervention mentor ten times during the program, where he "expressed disturbing views, including views about causing harm and spoke about bomb making, explaining that he had accessed the Dark Web", the prosecutor told the court.
On 16th August 2017, the intervention mentor gave the defendant a warning about section 58 of the Terrorism Act 2000 and told him the material he had been accessing "put him at risk of conviction", the court heard.
Four months later the defendant is alleged to have burnt a CD containing a “substantial body of material” on bomb-making.
In April 2017 as an army cadet, the defendant attended a weekend camping trip where he "brought with him a knife" and "used it to slash tents, frightening the female occupants and causing damage", the prosecutor said.
As a result, he was dismissed from the cadets, the jury was told.
The defendant pleaded not guilty to one count of making an explosive substance with intent, one count of making an explosive substance and three counts of possession of a document 'likely to be useful to a person committing or preparing an act of terrorism'.