Five teenagers are facing jail for the killing of a 15-year-old boy "hunted down" and stabbed at a Tube station in an attack planned on Facebook.
Rush-hour commuters looked on in horror as Sofyen Belamouadden was chased across a concourse at Victoria station in London by 20 youths charging at him with weapons including a samurai sword.
The schoolboy tumbled down a flight of stairs into an Underground ticket hall where he was surrounded, punched, kicked, and knifed repeatedly as he lay helpless on the floor.
Obi Nwokeh, 18, and a 17-year-old youth were convicted of murder and three others found guilty of manslaughter by an Old Bailey jury.
The "merciless" attack took just seconds, during which Sofyen was stabbed nine times, with such ferocity that one blow cut through his heart and into his spine.
The violence in March last year was the result of "simmering tensions" between pupils from two west London schools, the court heard.
Sofyen, from Acton, west London, was targeted in revenge for a boy being given a bloody nose during a skirmish at the station the day before. This time the victim and his friends were "hopelessly outnumbered" and not expecting the "level of ferocity" they were to encounter.
Nwokeh, of Bermondsey, and the 17-year-old were convicted of murder by unanimous jury verdicts. Samuel Roberts, of Camberwell, Adonis Akra, of Stockwell, both 18, and another 17-year-old were cleared of the charge but convicted of manslaughter. Enoch Amoah, 18, of Camberwell, was cleared of both charges but convicted of violent disorder.
All six defendants were found guilty of conspiracy to cause grievous bodily harm.
A number of other youths are due to face separate trials over the killing.