Firearms officers descended on the building in Kensington, central London, at about 11am on Friday. "One person, who is believed to be behind the incident, has been arrested and at this stage we are not at this stage looking for anyone else".
One person has been arrested, police confirmed, and teams of armed officers attended the scene.
Their investigation is ongoing.
Neither of those stabbed suffered life-threatening injuries, Scotland Yard said.
Eyewitness Maithreyi Seetharaman told CNN that she could see around a dozen police cars, multiple armed officers and two ambulances at the scene as the incident unfolded. He was pronounced dead at 8.15pm, the Metropolitan police said.
Two arguing chefs fought with knives inside Sony's headquarters in west London today, sparking fears of a terror attack as pop stars and employees fled the building screaming.
Staff were evacuated from the building on Derry Street, just off London's Kensington High Street "as a precaution", police said.
Pictures on social media showed large numbers of police vehicles at the scene. "Now, this is something people should take seriously, before any more kids, young children or anyone dies in this way". She went to Morley's after a friend told her about the incident.
'We treated two people at the scene. There is no evidence of any firearms involved.
"Gradually they started to release people in tens, twenties, [and] a stretcher turned up with all the medical kit on it, but just stayed outside".
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