Three teenagers were being questioned today on suspicion of murdering a schoolboy in a gang knife attack.
Detectives were optimistic of making several more arrests as neighbours came forward to identify attackers who set upon 15-year-old Temidayo Ogunneye.
Among witnesses to the "horrible" attack was a nine-year-old girl who screamed in terror as she watched the stabbing on a leafy south London street.
Another local told how a teacher at a nearby school in Camberwell had tried to step in to break up the violence.
Resident Nimo Jama, 38, said her niece watched from her bedroom window as Temidayo was stabbed in broad daylight.
She said that a group of about 10 black teenage boys and four or five girls were gathered before the youngster was left "in a horrible state".
Ms Jama said: "He wasn't moving or blinking, his eyes were just wide open and he was barely breathing."
She said the victim's friend used a scarf to stop the blood and was screaming his name.
"There was blood everywhere. It was terrifying," she added.
One woman, who did not wish to be named, said a fight had broken out between two sets of rival gangs and the teacher from a nearby school stepped in to stop the fight escalating.
The boy, who lived with his family in Peckham, was pronounced dead at 10.30pm on Wednesday - six hours after he was taken to hospital from Cormont Road.
Family members were informed as police made a string of arrests overnight.
Temidayo, the fifth teenager to be stabbed to death in the city this year, suffered stab wounds to the body, emergency services said.
Police are still trying to establish a motive for the attack.
Detective Chief Inspector John McFarlane of Scotland Yard's homicide and serious crime command said there had been "quite a disturbance" in the wake of the attack.
"A large number of youths were hanging around the area," he said.
He said three teenagers were arrested on Wednesday night and were being held in custody at a local police station.
"I need the assistance of anyone who would have seen the youths running away from the scene," he added.
The quiet road where the boy was found was cordoned off yesterday morning.
Residents said they were in shock.
Police and the ambulance service were called at around 4.15pm on Wednesday to the rear of Calais Gate.
A post-mortem examination will take place.
Police are asking anyone with information to contact the incident room on 0208 721 4205 or, to remain anonymous, call Crimestoppers on 0800 555 111.