A man has died after being shot during an "intelligence-led" police operation in north London.
The man was shot in Bracknell Close, Wood Green, at around 9am, Scotland Yard said.
Four men have been arrested are being held at separate police stations in the capital.
Two were detained near the scene on suspicion of conspiracy to facilitate the escape of an individual from lawful custody.
Scotland Yard said the operation was not related to terrorism.
Witness Nick Lindsay, a workman who was surfacing a road nearby, said the man who was shot was sitting in his car when police moved in.
He told Sky News: "The police all came down, they all jumped out of cars with their guns and said, 'Get down', and then there was a smash, then the gun shot went off. By that time police officers grabbed us to move us out of the way."
Mr Lindsay said the incident was over in 10 to 15 seconds, but the man had been in the car for around 30 minutes before the police swooped in.
He said: "He was parked there for easily half an hour, I would have said, because he was there when we first turned up this morning. He must have been there at least half an hour, minimum."
The Directorate of Professional Standards - the Metropolitan Police's internal investigator - has been informed of the incident and investigators from the Independent Police Complaints Commission (IPCC) are also at the incident.
Paramedics and an air ambulance were called to the scene, where police earlier cordoned off a section of road around the junction of Bracknell Close and Olympus Grove, near Winkfield Road.
A white forensics tent was erected near an ambulance in the residential street, which is lined on either side with cars, and plain clothes officers were seen with evidence bags.
Officers wearing balaclavas were also at the scene, as were police cars and 4x4 vehicles with blacked-out number plates. The shooting took place just a few streets from Wood Green Crown Court.
IPCC representatives will attend a post-incident debrief, expected later today, in which the officers involved will give an account of what happened during the shooting.
It is the fourth time in recent months that the IPCC has investigated police-related shootings in London.
Joseph Hive, 28, was Tasered a number of times and shot by police in Brent on October 8. He was later charged with robbery and other offences.
James Fox, 43, was shot dead by police at a block of flats in Enfield, north London on August 31. Armed officers stormed the sixth floor after receiving reports a man with a gun was threatening to shoot someone, and a non-police firearm was later recovered.
And the IPCC is investigating an incident on August 21 when a 34-year-old man was shot and injured by officers in south Clapham after a stand-off lasting several hours. A firearm was later recovered.