Felix Winter, now 18, was described in court as having “idolised” the perpetrators of the 1999 Columbine High School massacre, in which 12 students and a teacher were killed. Winter repeatedly spoke of mounting a similar “Doomsday” attack and harboured racist and pro-Nazi views.

He admitted two charges – a breach of the peace and an offence under the Terrorism Act – at a hearing in February. The offences were committed between June 2022 and July 2023, when he was aged 15 and 16.

Shelagh McCall KC, defending, argued for a community-based alternative to custody, describing Winter as having mental health difficulties.

She also noted that he is transgender, and asked the court to account for this during sentencing.

The High Court in Glasgow heard that Winter had been “radicalised” after spending more than 1,000 hours in contact with an extremist group on Discord. Lord Arthurson said Winter had engaged with the pro-Nazi group online for approximately two hours a day over the course of two years.

He also shared his intentions with fellow pupils, speaking of a graphically detailed plan to carry out a school massacre. In a January 2023 journal entry, he described his school as a “virus upon this earth” and wrote that he would soon prove that “I am a God”.

Lord Arthurson added: “The whole material available to me indicate that you were progressing towards the brink of perpetrating a mass school shooting, you were radicalised and your statement of intent could not be clearer.”

Winter, from Kirknewton in West Lothian, had been referred to the UK’s Prevent counter-terrorism programme – on four separate occasions. The scheme requires public bodies, including schools and police, to identify and support individuals at risk of being drawn into extremism.

Police Scotland began investigating in summer 2023 after a photograph of Winter in combat clothing with an imitation firearm circulated online, alarming pupils and parents. The outfit and prop were later found to have been issued for a school drama project in which he played a kidnapper.

However, officers uncovered evidence that Winter frequently spoke to other pupils about launching a school attack and had “exhibited a variety of alarming behaviours” over a 13-month period.

He was detained under the Terrorism Act on 9 July 2023 as he returned from a family holiday. On searching his electronic devices, police found files relating to “homemade” firearms and poisons, along with a TikTok account showing him in black combat gear and a skeleton mask.

The court heard he had amassed 65 videos about the Columbine massacre, some set to music that appeared to “glamorise” the killings. Pupils reported that Winter spoke of using firearms, explosives or poison to attack students and staff, and had even expressed interest in acquiring a 3D printer to make a weapon.