Duncan Kennedy
BBC South of England Correspondent

It seems to have started to unfold from about 14:00 GMT, but reports are still contradictory.

It looks like a man went into a shop with a knife and started stabbing people.

The reports then go on to suggest that the man came out of the shop and stabbed a woman - possibly on a bicycle.

At that point it seems the alarm was raised and the police arrived incredibly quickly.

It seems to be pretty clear three shots were fired by the police to bring this incident to a halt.

BBC Newsbeat journalist Steffan Powell lives near to where the incident took place.

"There is an eerie silence in the area at the moment," he says.

"Things are definitely quieter than it was an hour ago.

"We are still in lockdown - my neighbour tried to leave but was told quickly by the police to get back inside.

"I popped my head out of the window but it looks like the beginnings of forensic activity by the police has started."

One witness filmed the moments after armed police shot a man dead in Streatham. Watch the footage below.

Image source, PA Media

Richard Mustonen-Smith, 59, a response pastor for the Christian organisation Ascension Trust, told PA news agency he was "shocked" it had happened in Streatham, where he lived.

"We're always getting accidents down here but not this.

"My grandson was in the Odeon and they got told to go out the back because there was a bomb - they got them to go out of the back of the cinema."

Dan Johnson
BBC News

Now the police have contained the incident, there are a whole plethora of things for them to start investigating.

How much work will this person have done in terms of covering their tracks? How easy will it be to find out who they were?

Who they may have communicated with? What CCTV evidence is there?

It will takes days to build up a full picture.

Who else do they need to talk to in order to get information? Was this man on the radar of MI5? Was he known to the police?

The first thing will be to find out who this person was and what their background is.

Witnesses have described seeing a police car crash as the incident unfolded.

Adam Blake said he was walking along Streatham Common when he heard a loud bang.

"I heard a big crash and as I looked over, I heard a second big crash.

"Two to three cars crashed into each other and one was an unmarked police BMW," he said.

"Another police car carried on towards the hill, it was obvious they were pursuing someone towards the high road."

He said the incident happened before the shooting, at about 14:15 GMT and that a female police officer was injured.

One person said on Twitter they sheltered inside a branch of WH Smith on Streatham High Road as the incident unfolded.

"Heard the gunshots and went to the back of WHS looking for an alternative route out in case," they tweeted, external.

They added that police then evacuated them from the shop.

Image source, Daniel Gough

Eyewitness Daniel Gough said he was out for a run when he suddenly "heard three gunshots go off and everyone around me started running up a side street".

"I also ran with them and there was panic, people were yelling," he said.

"A young girl running alongside me kept asking ‘Is this what I’m meant to do’ - she was very distressed.

"After a few minutes I went back down and saw a policeman and he yelled, telling everyone to get back. His gun was pointing in the direction of a man on the floor.

"Then, suddenly, more police appeared. There were [officers] everywhere".

London Mayor Sadiq Khan says he is in "close contact" with the police following the incident in Streatham, and has praised the emergency services for their response.

In a statement, he said: "Terrorists seek to divide us and to destroy our way of life - here in London we will never let them succeed."

A large number of videos and photos of the scene are being shared on social media.

The sound of sirens can be heard in the background of most of the footage, while a helicopter can also be heard in other clips shared.

In one video, an armed response vehicle arrives in the middle of the road.

Several armed officers get out of the car and approach a man lying on the pavement outside a branch of Boots. The man does not appear to be moving.

The BBC's Steffan Powell witnessed the incident in south London and says there were armed police everywhere.

You can here him describe the scene in this video.

A spokeswoman for the London Ambulance Service said: "We were called at 13:58 today to reports of an incident in Streatham High Road.

"We are working closely with the other emergency services and are treating a number of patients at the scene.

"We will provide more details as soon as they are available."

Local resident Alanah Murphy has been talking to the BBC.

“I live at the top of Tooting where it becomes Streatham High [Road], my partner and I were on our way to Tesco when we saw a helicopter circle above us.

"It landed in front of us and ambulances began to swarm - we had no idea what had happened but assumed it was a car accident.

"As we walked further... we saw armed police arrive and begin to instruct buses to move around to hide a car.

"The police started screaming at everyone to get back and pushed the crowds back.

"A number of police and paramedics... began crouching in a circle, which we then believed was [around] a body, but we didn’t find this out till later."

A 19-year-old student from Streatham, who asked to remain anonymous, told PA news agency that he witnessed the shooting on Streatham High Road in front of a shop.

"I was crossing the road when I saw a man with a machete and silver canisters on his chest being chased by what I assume was an undercover police officer - as they were in civilian clothing.

"The man was then shot - I think I heard three gunshots, but I can't quite remember.

"After that I ran into the library to get to safety.

"From the library I saw a load of ambulances and armed police officers arrive on the scene."

He said people began running into nearby shops.

"We were all informed to stay in buildings by armed police, until we were evacuated," he added.

• Shortly after 14:00 GMT on Sunday, witnesses on social media reported hearing gunshots fired on Streatham High Road
• The Met Police said that a number of people were believed to have been stabbed
• Police said a man who was shot by armed officers died from his injuries
• The incident was declared as "terrorist-related" by police
• London Ambulance Service said they were attending the scene
• Many videos have been posted of the scene on social media. One recording - verified by the BBC - shows a man lying on the ground with at least three armed police officers holding firearms pointed in his direction
• The scene has been sealed off - with at least six police cars, two ambulances and half a dozen paramedic vehicles in attendance

Chris Phillips, the former head of the National Counter Terrorism Security Office, said the incident "looks very similar to what we saw on London Bridge just a few months ago".

"We can only hope that police have dealt with it fully now and that it's one person acting alone," he said.