The death of a 14-year-old boy stabbed in a park was recorded on his own mobile telephone, a court heard on Tuesday.
The 12-second clip showed how a row between two schoolboys on a sunny afternoon, escalated into death.
Leroy James had emptied his pockets, giving a girl his mobile, before squaring up to his 14-year-old rival as other children egged them on.
But, the Old Bailey was told, the second, and smaller, boy, kept his right hand in his trouser pocket.
As the boys struggled, Leroy's white T-shirt was stained with his blood after he was stabbed in the heart.
Soon after, youngsters called out to him that he had been "bored", and Leroy suddenly collapsed on to his back.
The footage was shown to jurors as the second boy, now aged 15 and who cannot be identified for legal reasons, denied murder and having a knife as an offensive weapon.
Leroy James died in August last year, at a play area known as The Gym in Ponders End, north London, where equipment was arranged in the shape of the Olympics logo.
Duncan Penny, prosecuting, said: "Whilst he remained on his feet for a few more seconds, soon he fell and his lifeblood ebbed away."
The defendant liked to describe his blade as his "pet" or "alligator", the court heard.
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.
The defendant had allegedly 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."