A 15-year-old boy is facing a life sentence after being found guilty of killing a schoolboy whose stabbing was recorded on his own mobile phone.
Leroy James, 14, was knifed in a park by Mustafa Gurpinar who was also 14 at time.
Gurpinar had challenged Leroy to a fight in a local play area in Ponders End, north London, in August, last year, on Facebook.
Mustafa Gurpinar stabbed Leroy James
But he pulled a knife out of his pocket when the larger boy got the better of him, the Old Bailey heard.
Before the confrontation, Leroy handed his phone to a girl who videoed his death.
Gurpinar was found guilty of murder by a 10-2 majority, and guilty of having a knife as an offensive weapon.
He was remanded in custody to be sentenced in September.
Judge John Bevan told the jury the trial in parts had been "horrendous". The two boys had been "extraordinarily young", he said.
Judge Bevan told Gurpinar that the starting point for his minimum sentence was 12 years.
The trial was told that Gurpinar, who called his knife his "pet" or "alligator", showed an obsession with knives.
The disturbing 12-second clip of the attack was shown to jurors.
It showed how a row between two schoolboys on a sunny afternoon, escalated into murder.
Other youngsters egged the two boys on. But as they struggled, Leroy's white T-shirt became stained with his blood as he was stabbed in the heart.
Soon after, youngsters called out to him that he had been "bored", and Leroy suddenly collapsed onto his back.
Duncan Penny, prosecuting, said: "Whilst he remained on his feet for a few more seconds, soon he fell and his lifeblood ebbed away."
Mr Penny told the jury there had been bad feeling between the boys, possibly about a girl, and others were egging them on to fight.
"To those who were watching, what was expected to be a fist fight transpired to be anything but," said Mr Penny.
Gurpinar had told a friend on Facebook: "If you see me on road... and I have my right hand in my pocket dat means I have a knife."
Mr Penny said: "This was a blade which the defendant liked to describe as his 'pet' or his 'alligator'.
"It was wielded swiftly and lethally."