A 60-year-old man has been stabbed to death in a residential street in south London.
Police and ambulance crews were called to reports of a stabbing in Woodcroft Road, Thornton Heath, Croydon, at 21:30 GMT on Monday.
The victim was found outside a property with knife injuries and was pronounced dead at 21:49, the Met Police said.
A 50-year-old man was arrested at the scene on suspicion of murder and taken into custody.
The suspect became unwell while in custody and was transferred to hospital where he is in a stable condition, police said.
Det Ch Insp Simon Harding said: "The victim was found injured in a residential street. While it is not a heavy footfall location, there may have been members of the public travelling through Woodcroft Road who saw something.
"I urge those people to come forward and speak to my officers without delay.
"No matter how insignificant you think it may be please do make the call.
"We are building the sequence of events leading up to and immediately following this attack which has led to a man's death, your call could complete the picture."
Inquiries into the circumstances continue.