Four men questioned
Detectives were questioning four men over a suspected gang fight in which one teenager was stabbed to death and another seriously injured.
Residents said members of two rival gangs clashed on the Lansdowne Estate in Lambeth, south London, on Monday night.
They described a running battle on the sprawling estate which ended with the fatal attack in an alleyway linking it with Larkhall Park.
One neighbour said the victim's sister ran to the scene and was held back by the emergency services.
The teenager, who asked not to be named, said: "There was a boy injured. His sister was there, screaming. She said, 'He's my brother. I want to hug him and I want to kiss him. He cannot be gone'."
Several witnesses said a Staffordshire bull terrier-type dog was also stabbed during the fight.
One man, who works as a youth football coach in the park, said it was sparked when teenagers who live on the rival Heman Estate strayed into the area.
Many residents said they heard shouting and screaming shortly before 8.30pm on Monday evening.
Metropolitan Police officers and London Ambulance Service paramedics were called as a police helicopter hovered overhead.
One boy, aged in his mid to late teens, died at the scene while a second was taken to hospital with stab wounds. His condition was described as stable. THE ECHO