A man in his 60s has been stabbed to death in west London.
Emergency services were called at 18:40 BST on Saturday to St Mary's Avenue South in Southall, where the man was pronounced dead, the Met Police said.
A man in his 30s has been arrested on suspicion of murder and is in hospital under police guard being treated for minor injuries.
According to a witness who gave the injured man first aid, he was stabbed after leaving a pub.
Raj Grover, who lives near the victim, said he was getting ready to go to his own birthday party when the man knocked on his front door.
"He was ringing our doorbell," he told the Press Association. "He rang the bell and I went out, my son was there, he was shouting 'Dad, come out'.
"I went downstairs and saw he was full of blood, and then I was running to pick up a towel.
"I put the towel on and I was pressing to stop the blood, then my wife came out, we called the ambulance and the police."
Mr Grover, who runs a local business, said the victim asked him to call his wife, who then arrived at the house.
"His wife, she mentioned he went to the pub, I don't know what happened in the pub just around the corner, he came back, was on his way back and somebody stabbed him twice, stabbed him two times with a knife on the stomach and on his side," he said.
The Reverend Dave Bookless, the vicar of St Mary's church which is opposite the street, said the killing had come as "a huge shock" as the area has "quite a village feeling".
"A lot of people are saying this is not the kind of area this happens," he said.
Scotland Yard said a crime scene remained in place but some local roads had reopened.