Jamil Palmer stabbed to death after footage of him knocking out rival was posted on Snapchat Jamil Palmer 'had knocked out 17-year-old rival in Feltham, west London' Footage of the boy lying unconscious 'was circulated on Snapchat' Mr Palmer then challenged boy to a second fight in a park, court heard But rival 'brought along four other teens who helped murder Mr Palmer' Kingston College student died in hospital of a stab wound to the heart Kishon Zelaya, 18, and four teens aged 17, 16, 16 and 15 all deny murder Killed: College student Jamil Palmer, 18, died after he was stabbed in the heart in a London park Four teenage boys and a girl murdered an 18-year-old student after footage of him knocking one of them out was shared on Snapchat, a court heard. Jamil Palmer died of a stab wound to the heart after an altercation in a park in Feltham, west London, on May 6 this year. Yesterday a court heard he had 'humiliated' a 17-year-old rival by knocking him unconscious just hours before the fatal stabbing - while a friend filmed on a mobile phone. The footage was shared on the mobile app Snapchat, which allows users to 'broadcast' brief video clips to hundreds of friends at once. Following the fight - which happened outside a youth court where both teenagers appeared over a separate incident - Mr Palmer is said to have challenged his rival to a one-on-one follow-up. He invited the 17-year-old to meet him in Crane Park, Hounslow, later that day. But Snaresbrook Crown Court was told the 17-year-old brought along three other boys aged 18, 16 and 15 - along with a 16-year-old girl - who all murdered Mr Palmer. The jury heard CCTV footage showed the four boys and the girl arriving at the park. Minutes later Mr Palmer suffered three stab wounds and was found slumped near the entrance to a cul-de-sac. The Kingston College student from Hampton, Middlesex, was taken to hospital where he was pronounced dead. The court heard Mr Palmer and his rival were outside Feltham Youth Court when the initial fight took place. They were there because they had been charged with affray following an incident outside the Hounslow Youth Offenders Team office on February 25. The 17-year-old rival has declined to give evidence in his defence, as has 18-year-old Kishon Zelaya, who is the only defendant old enough to be named. But the 15-year-old, of Wembley, north west London, took the stand in his defence yesterday.Â He told the jury he and the other four teenagers had laughed at the Snapchat video, but the 17-year-old was complaining he had been hit from behind. Showdown: Mr Palmer was said to have invited his rival to a 'one-on-one' in Crane Park, Hounslow (pictured) -- but the 17-year-old brought three boys aged 18, 16 and 15 along with a 16-year-old girl. All deny murder John McGuiness QC, prosecuting, asked the 15-year-old: â€˜Did you understand from that, that Jamil had won the fight? Was [the defendant] saying it wasnâ€™t a fair fight because Jamil had hit him from behind?â€™ He replied: â€˜He said he got hit from behind.â€™ Mr McGuiness said: â€˜Was he angry that it hadnâ€™t been a fair fight?â€™ Did he tell you why he wanted you to come with him? The defendant replied: â€˜Noâ€™. Mr McGuiness asked: â€˜Did he feel a bit humiliated? Because this was filmed on a phone this suggests that someone had been standing over him at the time of the fight and taking a video of him - what this shows is that they had had a fight and Jamil had knocked him out. â€˜What did you think when you saw the video? Did you think the defendant was going to get the best of Jamil? Theyâ€™d had a fight and Jamil had knocked him out, and now Jamil wanted another fight didnâ€™t he? So how is he going to get the best of Jamil? But the 15-year-old insisted there had been no mention of knives or weapons. Zelaya, of Reading, and the other four defendants of Hounslow, West London, and Wembley, north London, all deny murder and an alternative charge of conspiracy to cause grievous bodily harm with intent.