A 16-year-old youth has been found guilty of stabbing his former friend to death with a meat cleaver after a row on Snapchat spiralled out of control.
The boy, who cannot be identified, had sent laughing emojis during a group chat on the social media app when 16-year-old Osman Sharif Soufi, claimed he was the toughest - or "certier".
The following day, the two boys met up in Tottenham in north London armed with a knife and a hammer, and within hours, Osman was dead.
Following at trial at the Old Bailey, the defendant, who had been hoping to study plumbing at college, was found guilty of his murder and possession of a knife.
The defendant slammed his fists into the dock as the jury convicted him of murder by a majority of 11 to one after more than 15 hours of deliberations.
Adjourning sentencing for reports until January 26, Judge Nicholas Hilliard QC told jurors it was a "desperately sad" case which had devastated the victim's family.
He said: "This demonstrates yet again the terrible problem we have with young people and knife crime."
The court had heard how the pair had known each other from around the neighbourhood for about two years before the killing on June 6.
Osman took offence at being mocked in front of the group on Snapchat and the argument rapidly escalated.
The student had allegedly threatened to "wet" (stab) the defendant, give him a "drilling" (beat him up) and "rise the burning" (get a gun), according to another boy.
The following day, the defendant armed himself with a 31cm knife and went to Tottenham Green to confront the Osman, who had a hammer, according to witnesses.
The pair argued and witnesses claimed the defendant was waving his knife around before they split up and went separate ways.
Ten minutes later, they clashed in nearby Tynemouth Road and the youth stabbed Osman in the chest, causing devastating injuries.
The knife passed down through Osman's rib, damaging his heart, lungs and liver and became embedded in his body.
The defendant fled to the Broadwater Farm Estate then went to grandparents' home and changed his clothes.
But his father called police and reported his son had been in a fight and he was arrested.
In a prepared statement, the youth told police he had closed his eyes and Osman had run into him while he was holding the knife.
Giving evidence, the defendant, who sat in court with his mother, claimed it was an accident and also that he was acting in self defence and did not mean to do him serious harm.