A boy of 16 died in his brother’s arms yesterday after confronting a youth who was threatening staff in a baker’s shop in south London.

Jimmy Mizen had gone to the Three Cooks bakery in Burnt Ash Hill, southeast London, with his brother Harry, 18, where according to witnesses a youth had been thrown out for arguing with staff. The attacker returned moments later and threw an advertising board through the glass door of the shop.

Broken glass hit workers, cutting the face of the female manager. Jimmy confronted the boy and according to his father was struck in the neck with a glass dish. As the attacker fled, Harry called his older brother Tommy.

“I found him collapsed on the floor,” said Tommy, 24. “I did what I could; he was still conscious and his eyes were open. I think he could understand what I was saying, but he was just murmuring. It was hideous. He had a cut down the side of his neck. I think he was dead by the time they [the paramedics] arrived.”

Jimmy had turned 16 on Friday and was due to take his GCSEs at the St Thomas More Catholic comprehensive school in nearby Eltham, of which his father, Barry, is vice-chairman of the governors.

His father, 56, said: “It was mindless violence, just pure aggression. A fellow picked up a glass dish and smashed it against the side of his neck. We’re told he bled to death.”

His mother, Margaret, 55, said: “Jimmy was the loveliest, gentlest giant. He was loved by everyone, by his school, the church and his family.”

Jimmy was one of nine children and played rugby for Sidcup. His father said he had gone out to buy a lottery ticket yesterday morning. “He wanted to play the lottery for the first time because he’d just turned 16. It was part of his birthday celebrations.”

Witnesses said Jimmy’s attacker had been thrown out of the bakery for arguing with staff and returned moments later to throw an advertising board through a window.

Matthew Fletcher, an eyewitness, said: “I heard a smash and saw a boy with a sign smashing the shop door, kicking it through.He’s forced his way into the shop, run behind the counter and was hitting somebody with the sign. I see somebody in a blue polo top trying to stop him.”

Ali Patel, a pharmacist at the chemist next door, said: “That shop is mostly run by women and I think he was trying to be brave and sort the mad kid out.”

Last night about 30 family and friends made the short walk from the family home to the scene and laid flowers at the spot where Jimmy had died.

Jimmy’s distraught parents, who have a shoe repair shop where Jimmy helped out on a Saturday, hugged each other.

At the Our Lady of Lourdes Roman Catholic church, where Jimmy worshipped and had been an altar boy, a minute’s silence was held in his memory during the evening mass. “I would see him all the time at Sunday mass,” Father Edward Perera said.

“He was such a kind, quiet and gentle lad. Even as a teenager he would come to our family days and offer his support. He was very much part of our parish family.

“It’s a large family but they are all very close to each other and to the church.”

Catherine Busby, 87, a neighbour, has known the family for 30 years. “He was a beautiful boy – they’re a beautiful family,” she said. “They are all very, very good to me. Jimmy was going to cut my grass tomorrow.”

Jimmy is the 13th teenager murdered in London this year. Last night his father called on Boris Johnson, the capital’s new mayor, to act on his pledge to “lead the fightback” against violent youth crime.

“This is the result of mindless, bloody violence, which is all too common these days,” Barry Mizen said. “Boris Johnson was elected by promising he was going to cut down on street violence, and today has proved this is something that he really has to do. My son was 16 yesterday, he was doing well at school and nobody had a bad word to say about him.”

Peter Eastwood, 64, a governor at St Thomas More school, said: “He was a thoroughly likeable boy who had been working incredibly hard towards his exams.”

Jimmy’s school friends paid tribute to him last night on a website. James Cobby wrote: “I can’t believe it mate! You’re gone. I will never forget you mate, all the laughs you gave me will always be kept close to my heart. Love you for ever and ever.”

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