King Charles’s “thoughts and prayers are with all those affected” after a sword attack in north-east London, Buckingham Palace has said.
A boy of 14 died in Tuesday’s attack in Hainault. Four people including two police officers were injured.
The Palace said the King’s thoughts were particularly with “the family of the young victim” who lost his life.
A man, 36, was arrested and is in hospital being treated for injuries sustained when a vehicle crashed.
The Metropolitan Police said the condition of the man, who was arrested on suspicion of murder, meant he had not yet been interviewed.
Police say they do not believe the attack was terror-related and was not a “targeted” attack.
They were called to reports of a car crashing into a house and people being stabbed at about 07:00 BST on Tuesday.
The suspect was then seen leaping over people’s garden fences and walking around with a sword. He was eventually cornered and Tasered in a front garden.
Footage shared on social media showed a man with a long knife in Laing Close.
Witness James Fernando said he had seen the suspect ask one of his neighbours to take his phone and “tell whoever was on the phone his location”.
The 39-year-old said the neighbour had soon noticed the sword and started running.
As she fled, the woman shouted to another neighbour, a boy on his way to school, who was then struck by the attacker as he turned around, he said.
Other eyewitnesses saw the suspect leaping over people’s garden fences, before he was eventually tasered by police.
The 14-year-old boy died from stab wounds shortly after being taken to hospital. His identity has not been released and his family are being supported by trained police staff.
Two other members of the public are still in hospital but their conditions are not considered to be life-threatening, say police.
Two Metropolitan Police officers have “significant but not life-threatening” injuries and will require surgery, the Met confirmed.
Police said they were not looking for any more suspects.
They added that there had been speculation about the man’s background including police contact with him. They said police checks had found no trace of a prior incident involving the man.
Mayor of London Sadiq Khan said: “I’m sure I speak for the entire city when I say our thoughts are with this young child and his family.”
He said additional uniformed officers would be in the area over the coming days and asked residents in Hainault to pass on any footage recorded on phones or doorbell cameras to the police.
Prime Minister Rishi Sunak described the incident as “shocking”, adding: “Such violence has no place on our streets.”
Wes Streeting, the MP for Ilford North, said the community would be “devastated by the heartbreaking news”. Thanking the emergency services for their “courageous response”, he described the officers who had put themselves in harm’s way to protect others as “the best of us”.