A murder inquiry is under way after a teenager was stabbed to death in south-west London.
Police were called by the London ambulance service at 4.15pm on Tuesday to an address in Wayford Street, Battersea, to reports of a stabbing.
The man, aged 18, was pronounced dead at 5pm.
He has been named locally as Matthew Kitandwe, a promising footballer, and friends have set up an online fundraising page for donations towards his funeral.
An 18-year-old man was arrested on suspicion of murder and remains in custody in south London.
Gary Knight was at his home on the same street when he heard sirens from an approaching fire engine. Shortly after, he saw police cars and an ambulance arrive, and a stretcher being carried into the block of flats.
The 30-year-old Australian said he had only been living in the flat he shares with his wife for around three months but that it "seems like a really nice area".
"The only thing I did notice was there was a group of maybe three kids in hoodies and on a bike," he said.
"They were milling around that particular block and it was a weird spot where kids have never hung before, so I don't know if that's got anything to do with it but I remember seeing them maybe 20 minutes before I heard the first fire siren."
Later, he said: "People who knew the kid had come to the scene, and one kid in particular was sort of crying very loudly and screaming - lamenting I guess. So he must have been a friend or something like that.
"He had two friends with him - a girl and a boy - that were sort of consoling him, but then he got on his push bike and left so I don't think he lived here or anything.
"I saw an older black male later on crying, and another woman with him - they must have been family or something, they ended up getting clothes from the apartment.
"Whoever's killed him must know them because they got entry to their flat through a security door and their own door. You can't just walk up the stairs, you've got to have a security key to get on to the stairwell," he added.
Next of kin are aware but the body is yet to be formally identified, police said.