A public school pupil has been found guilty of attacking two of his roommates with a hammer that nearly killed them.

The boy was aged 16 and a student at the £45,000 Blundell’s School at Tiverton when he attacked the victims, then aged 15 and 16, as they slept at 12.50 am on June 9 last year.

He used one of his hammers to attack 39-year-old housemaster Henry Roffe-Silvester as he went into the three-person dormitory to investigate the noise. He suffered less serious head wounds.

The defendant, now aged 17, was found guilty of three counts of attempted murder after a jury at Exeter Crown Court rejected his defence team’s claim that he had been sleepwalking when he carried out the attacks.

The boy, who has autism, will now undergo further psychological and psychiatric examinations before Judge Mrs Justice Cutts decides on a sentence next month.

During a ten-week trial the jury heard how the boy developed grudges against both of his dorm-mates for different reasons and had slipped into a lifestyle in which he spent many hours online at the expense of his schoolwork and his relationships with other pupils.

He had researched child serial killers, and hammer attacks on sleeping victims and spent hours watching horror movies and reading conspiracy theories about zombies, some of which suggested that bug tech firms had planted chips in people’s heads to control their brains.

The attacker said he had accumulated an arsenal of hammers, knives and a shard of broken mirror to protect himself against what he called a ‘zombie apocalypse’, but also told fellow pupils after the attack that he had been dreaming when he carried it out.

His claims to have been sleepwalking were undermined by evidence from his iPad, which he had been using until seven minutes before the assault, using a toggle on his headphones to replay the Robin Hustin's song 'Light It Up' three times.

He had also been watching a horror movie called 'The Haunting of Hill House' into the early hours. An expert told the court that sleepwalking does not start until about 40 minutes after someone falls asleep.

A defence sleep expert took the opposite view, saying that Mr Roffe-Silvester’s description of the boy was a textbook example of sleepwalking and suggesting he may have gone straight into deep sleep because he was sleep-deprived and highly stressed.

The attacks left both victims with serious head injuries, the younger boy suffering 14 skull fractures and the older boy at least five. Both were taken to Musgrove Park hospital in Taunton but moved to Bristol Children Hospital for specialist treatment.

They had some brain injuries and internal bleeding but survived in large part due to the first aid they received from a fellow pupil who acted under instructions from a 999 operator until paramedics arrived.

The victims were both sleeping in raised cabin beds, meaning that the attacker had to climb up while holding at least one hammer, before he started hitting them.

The boys have both made good recoveries and were back at Blundell’s when police carried out further video-recorded interviews in October.

The defendant had been caught with a hammer during a room inspection the term before the attacks took place. It was confiscated but was returned at the end of term with the intention it should be taken away.

He kept it and added two more claw hammers which he bought from a hardware shop in Tiverton for £1 each. He had previously threatened another pupil with a hammer but it had not been reported to staff. The hammers were kept in a locked cupboard in the dormitory which also contained other weapons.

The younger victim had reported being bullied by his attacker, who the school had planned to move to another room in the Peterhouse boarding house when a space could be found.

The two boys had been close friends the previous year but fell out after the 16-year-old felt he had been mocked by the younger boy over a school project.

He embarked on a campaign of harassment that included sending nasty texts during the holidays, smashing up his school folders with a hammer, and throwing his stationery out of the dormitory window.

In messages sent through a gaming website, he told him he hated him and sent him a photo of a smashed head with brains coming out of it. He also sent a still from the horror film The Texas Chainsaw Massacre. Other messages said ‘f***ing die’, and ‘f***ing hate you, die’.

The attacker also had a grudge against the other roommate, who had scrawled an offensive message in marker pen on a bottle.

Police experts who investigated the defendant’s online activity discovered that he was being blackmailed for £1,000 by an untraceable sextortion gang which had lured him into sending indecent images of himself and was threatening to send them to friends or family.

The inquiries also found a disturbing chain of internet searches into hammer attacks. He had researched serial killers and sentences for murder on the internet.

He had carried out internet searches in the five preceding months including ‘Can a hammer be used as a weapon? Can a hammer kill? What would happen to the head if someone was hit by a hammer, would they lose consciousness?’ and ‘What happens to a head when it is hit by a hammer’.

The boy also researched serial killers and what weapons they used. Searches included ‘young serial killer near Exeter, ‘youngest serial killer’, how do serial killers get caught’ and ‘serial killer kills victim while they are asleep’.

He also looked up likely penalties for serial killers, where they would serve their sentences, and how would they be regarded by other inmates.