This is the chilling moment that murderer Mohammed Umar Khan dances in his school's canteen after stabbing Harvey Willgoose.
Khan, 15, was jailed over Harvey's murder on Wednesday - with a judge lifting an anonymity order so the extent of his crimes could be made public.
Now, South Yorkshire Police has released CCTV footage from All Saints Catholic High School, Sheffield, in February.
Video shows the moment Khan confronted Harvey, also 15, in a corridor before later brandishing his 13cm hunting knife - the murder weapon.
Sheffield Crown Court heard how other pupils fled "in fear and panic" after the fatal attack.
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