How killer Will Cornick planned ‘triple homicide’ at Leeds school

The teenager showed no emotion during the attack and displayed no signs of his murderous intent in the days leading up to it.

He had been a polite and academically bright pupil throughout most of his school life. But after being diagnosed with diabetes at the age of 12, there had been a noticeable change in his personality.

In a detailed explanation of his motivation, he told a psychiatrist: “(The killing) was always on my mind since Year 8; the thought of homicide, murdering her. I couldn’t see myself passing college and had no hope of doing anything. I tried to apply for the army but they said no because of my diabetes. I knew what I was going to do; it was what I did. I said I was going to do other stuff but I never got the chance, other murders. It was a triple homicide.”

At the time of the killing, the Year 11 pupil was studying for his GCSE exams, having taken and passed five exams a year early.

Prosecutor Paul Greaney, QC, described the youngster’s mum and dad, who have been separated and divorced for many years, as “decent people and responsible parents.”

He said: “They are at a loss to understand how and why their son has turned out as he has and they have co-operated fully with the police and with the prosecution.”

Psychiatrist Dr John Kent said of the youngster’s parents: “Both parents are in my view entirely responsible and caring people. They have both been devastated by events and neither has an explanation.”

When he reached Year 7 his parents received a letter congratulating him on his progress.

Mr Greaney said there were only five recorded incidents of misbehaviour at school prior to the attack.

He said: “The third, fourth and fifth all occurred in February 2014 and all concerned William Cornick’s imagined problems with Mrs Maguire and his dislike for Spanish lessons.” The court heard there was a major event in the youngster’s life when he was on a family holiday when he was aged 12.

He collapsed and was admitted to hospital and later diagnosed with diabetes.

The diagnosis had a major impact not only on his life but on his mood and personality.

The youngster then began showing disturbing aspects of his behaviour in front of pupils at the school. Many of them were focused on Mrs Maguire. He told one friend that he had hated Mrs Maguire since Year 7 and wanted her dead.

He spoke to another pupil of her being killed in “unpleasant circumstances.”

To other pupils he spoke of his plan to kill not only Mrs Maguire, but a young female teacher who was pregnant, as well as a male teacher. The youngster also spoke of “brutally killing” Mrs Maguire in Facebook messages during Christmas.

In February this year, Mrs Maguire told the teenager he could not attend a school bowling trip after he failed to do his Spanish homework.

His parents were later called in to a meeting during which the pupil made it clear that he hated Mrs Maguire.

He later posted a message on Facebook which read: “The one absolute ******* ***** that deserves more than death, more than pain, torture and more than anything that we can understand.”

He showed pupils the knife on the morning of the murder. He threatened to kill them if they told anyone about what he was planning to do. Cornick also told pupils that his plan included killing two other teachers.