In a shocking incident, an Indian-origin shopkeeper was killed after he refused to serve cigarettes to under-age UK teenagers at his shop in north London. Vijay Patel, 49, was attacked in Mill Hill area of the city on Saturday night and rushed to the hospital, where he died of head injuries on Monday. Patel's deathbed photograph, hooked up to a life-support machine, has been released by his family as part of an appeal to hunt down the suspects involved in the attack. "The Homicide and Major Crime Command continue to investigate an appeal for information about the events leading up to the incident which resulted in Patel's death. It is believed that three persons were involved in the incident," Scotland Yard said in a statement. Just before the attack, a shop-keeper had asked a group youths for identification to prove they were over 18 years age - the legal age limit for purchase of tobacco and alcohol in the UK. When they could not provide it, the group "became aggressive, threatening to vandalise the shop", the Police said, as per a PTI report. Patel came to the aid of his colleague and was punched to the floor outside before the teenagers fled. The shop worker was also punched and suffered minor injuries. "Vijay was the best human being you could have seen in the world. He was my right arm," said Abdullah Rahimzai, the owner of the shop who was also hurt during the attack. Patel was struck in the chest and fell backwards, hitting his head as he landed. He was found lying injured on the pavement outside his local convenience store named Rota Express. The London Ambulance Service rushed him to St. Mary's Hospital in London. Patel had moved to London with his family from India in 2006 and his wife, Vibha, was on a visit to India at the time of the fatal attack. The Police are appealing for witnesses to track down the remaining suspects in the case.