Ryan Bravo, 18, was with his two brothers and a cousin when he was shot in the back as he entered a Costcutter store in Camberwell Road, Walworth. A 19-year-old man arrested shortly after the shooting was being questioned at a south London police station.

Mr Bravo is thought to have become caught up in a dispute between rival gangs on Wednesday night when he became the 22nd young victim of violent crime in London this year.

As he was entering the store, two other black males barged past him and a number of shots rang out from the riders of three scooters, which had been driven along the pavement.

Witnesses claimed the helmeted killers appeared to be laughing and joking as they opened fire.

With blood pouring from his wound, Mr Bravo staggered into the shop. As horrified shoppers looked on, his brothers and cousin made desperate attempts to keep him alive. But his injuries were too severe and he was pronounced dead shortly afterwards.

Mr Bravo mother, Elfrida Kiffin, said he was a loving brother, partner and son who was already dearly missed.

In a statement, she said: "I would like to state that Ryan was a decent, hard-working young man and loving son."

DI Tim Carter, the officer leading the investigation, said detectives were investigating the possibility that the bullets were intended for the two men, who barged past the victim.

CCTV footage has been taken from the shop and surrounding area.

"It is a line of inquiry that the two men that barged past the victim may have been chased by the people on the mopeds. I would appeal to those two men to come forward," DI Carter said.

"It would appear to be a targeted shooting but the young man involved was not the target. It is a possibility that these two men were the intended targets. He is merely a young lad going down the road into a shop with his brothers and cousin and was hit by a bullet."

Police are still unsure of a motive of the attack, but are looking into the possibility of a link with an incident at around 4.30 pm in Myattsfield estate in Lambeth when a young man was shot in the legs.

Police are still trying to trace the victim's father, who is believed to be in Nottingham. Of the victim's mother, DI Carter said: "She's distraught. All the family are distraught."

Mr Bravo, his brother and cousin had been visiting another member of the family in Peckham and were on their way to Lambeth when they stopped off for provisions at the Costcutter.

An Albanian man in his 20s was in the shop at the time of the shooting, said: "I didn't think anything bad was going to happen because I thought they were joking and laughing. They didn't look scared or angry or anything. But then I heard shots, three or four. I've never seen anyone get shot before. It was like something out of a film. It was all over in about seven seconds. I just put all of my stuff down and ran out of the shop.

"A hysterical lady ran out after me. Two people ran out, got on mopeds and drove away. I'm lucky to be alive."

At Mr Bravo's mother Frida's home in Lambeth friends and family gathered to comfort each other. Mr Bravo's girlfriend described him as a "great guy".

She said: "He was a college student, studying business. He was completely innocent."

A family friend, who also did not want to be named, added: "He had so much to look forward to. He had his whole life ahead of him. It is just really, really sad."