A teenager winked and smiled at a fellow pupil before he stabbed a teacher to death in her classroom in Leeds, an inquest has heard.
Will Cornick showed the boy a kitchen knife just before he killed Ann Maguire at Corpus Christi Catholic College, Wakefield Coroner’s Court heard.
Mrs Maguire was stabbed seven times by the 15-year-old in April 2014.
In a statement the boy said Cornick asked if he wanted to touch the blade.
He said Cornick got the large knife out of his bag and asked “if I wanted to see how sharp it was”.
In a statement, he said the 15-year-old tried to hide the knife up his sleeve but said it was “too visible, too obvious” and changed his mind.
The teenager explained that he and Cornick were working in the room next to Mrs Maguire just before the incident.
He said then Cornick “just winked and smiled at me as he left the room”.
The boy said he then heard noises next door but said he was “in shock” and did not immediately report that Cornick had a knife.
“I did not really know what to do,” he said.
“I know I should have told someone, but in the room I was in there weren’t any teachers supervising us.”
The jury heard how Cornick told a number of children on the morning of the tragedy what he planned to do to Mrs Maguire and two other teachers.
Nick Armstrong, the barrister representing Mrs Maguire’s husband and their four children, has said how one of the key issues for the inquest is why none of these children reported what they had been told.
Cornick, who was 15 years old at the time of the incident, admitted murdering Mrs Maguire.
He was jailed for life and ordered to serve a minimum of 20 years in custody.