|PIC1|Police appealed on Sunday for witnesses to help find the killer of a teenage boy "of immaculate character" who died the day after his 16th birthday.

Jimmy Mizen bled to death following a frenzied attack after going to a bakers' shop in south east London on Saturday morning.

Mizen, who had gone out to buy his first lottery ticket, was the 13th teenager to be killed in London this year.

He died in his older brother's arms, his throat slashed by glass, after an unprovoked fight with a male youth who smashed his way into The Three Cooks Bakery in Lee.

Police said the youth had challenged Mizen to come outside the shop for a fight, and when Mizen refused, picked up an advertising board and smashed his way into the bakery.

"Jimmy was a person of immaculate character ... he is a victim of an entirely unprovoked and vicious attack," Detective Chief Inspector Cliff Lyons told reporters.

"This offence is not gang-related, this offence does not involve knives, this is about a very violent ... unprovoked attack on a decent young man," he added.

"For the sake of the family and this investigation I would like people to come forward with information."

Lyons specifically appealed for a middle-aged white man who was in the bakery at the time of the attack to contact police as a witness.

Passer-by Matthew Fletcher told the BBC he had seen the attacker force his way in.

"You could see him with a sign, smashing the shop door, kicking it through, he's forced his way into the shop and he's run behind the counter and from what I could see he was hitting somebody with the sign."

Police said they had searched a number of addresses in pursuit of the youth, who ran away from the scene through a nearby estate.

Mizen's family attended a service at the nearby Our Lady of Lourdes church where a two-minute silence was held.

After the service his parents paid tribute to their son as they hugged their other children outside the church.

"Jimmy is such a dear, dear young fellow," his father Barry told Sky television. "We're a decent family just going about its daily business."

His mother Margaret said she felt sorry for the killer's parents.

"I don't feel anger, I just feel sorry for the parents, because we've got lovely memories of Jimmy. They will have such sorrow about their son ... We've got wonderful memories of Jimmy that will go on for ever."

School friend Conor O'Hehir told the BBC Mizen was a "lovely person". He said he would never forget "seeing him at school, playing games with him, all those primary school games."

Other friends and strangers paid tribute to him on the Facebook social networking site, leaving messages on special "RIP Jimmy Mizen" page.

"Nowhere in London is safe anymore. I pray they catch the thug who did this. Rest in peace Jimmy," wrote Nina Ammundsen, who said she was a regular customer of the bakery where he died.