Mobile phone video footage of a London teenager allegedly murdering 14-year-old Leroy James has been shown to a jury at the Old Bailey.
In the 15-second video Leroy is seen arguing with the defendant, now 15, in a park at Ponders End in Enfield, north London, last August.
The defendant, who cannot be identified because of his age, denies murder and having a knife as an offensive weapon.
The video was recorded on Leroy's own phone, the court was told.
Leroy had emptied his pockets, giving a girl his phone before squaring up to the defendant, then 14, as other children egged them on, the jury heard.
The court was told the defendant however, kept his right hand in a trouser pocket, as the pair started to fight.
Moments later, Leroy's white T-shirt became stained with his blood after he sustained a knife wound to his heart, the court heard.
Soon after, youngsters called out to him that he had been "bored", and he suddenly collapsed.
The footage ended with a close up of him lying on his back, moments from death.
Leroy's family and relatives of the defendant sat on either side of the court as the video was played on a large screen.
Knife named 'alligator'
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 court was told the defendant 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."
Leroy died in a play area known as The Gym where equipment was arranged in the shape of the Olympics logo.