A teenager has been arrested on suspicion of murder following the fatal stabbing of a 21-year-old man at a shopping centre in north-west London.
Police were called to Brent Cross Shopping Centre at 6.45pm on Tuesday following reports of a group of males fighting.
Officers attended and found a 21-year-old man who had been stabbed.
Despite the efforts of officers, members of the public and ambulance staff, the man died at the scene.
The Metropolitan Police said it is likely a number of people witnessed the incident.
An 18-year-old man has been arrested nearby on suspicion of murder.
A second man, also believed to be aged 18, has been arrested on suspicion of affray.
Chief Superintendent Sara Leach, who is in charge of policing in north-west London, said: “My thoughts are with the loved ones of the young man who has been killed in this incident.
“I would like to offer my thanks to the members of the public who came to his aid. They showed considerable courage.
“Two people have been arrested and an investigation is already under way. We will do all we can to identify and bring to justice those responsible.
“The public can expect to see a heightened police presence in the area through the rest of this evening and in the days to come.”
The force urged anyone with information to call 101, providing the reference CAD6136/04MAY.