The mother of a "gentle giant" who died from a single stab wound on his own doorstep has spoken out as police renew appeals to find his killer.
Tina Ababio found her son, Andrew Oteng-Owusu, dying at the door of their home in Sharratt Street, New Cross, south-east London, on August 3.
She said: "Andrew was a very gentle, humble and polite young man, helpful to everyone he knew, especially in the neighbourhood.
"He was a wonderful carer for me and my only child and loved by everyone who knew him because of his nature.
"I don't understand who would be capable of taking his life."
The 19-year-old was Ms Ababio's carer as she is on dialysis.
He was stabbed on the other side of the Lovelinch Estate from his home, at the junction of Hornshay Street and Lovelinch Close, and managed to walk back to the flat that he shared with his mother.
Police are trying to trace a black man, aged between his late teens and mid-20s, who walked back to the flats with Mr Oteng-Owusu, who was found injured at around 11.40pm and died the next day.
Detective Inspector Mick Norman said: "The local community on the Lovelinch Estate have been really supportive but so far we really don't know why Andrew was stabbed to death that night.
"He has been described as a 'gentle giant' and he was a carer for his mother who is on dialysis. Andrew had not been in trouble with the police before and there are few clues as to why this might have happened.
"What we do know is that he was stabbed on the other side of the estate, at the junctions of Hornshay Street and Lovelinch Close. He then staggered home where he banged on the front door before collapsing.
"We are appealing for any witnesses or anyone with any information, no matter how small, to please come forward and help us solve Andrew's murder.
"In particular we are very keen to trace a young black man who, after the stabbing, walked with Andrew to the block of flats where he lived. He is aged in his late teens or early to mid-20s and was wearing a white T-shirt. If you can help, please approach us in confidence."
No arrests have been made so far and officers will be visiting the area on Wednesday to hand out appeal leaflets.
Anyone with information can call police on 020 8721 4961 or Crimestoppers anonymously on 0800 555 111.