A female police officer suffered “horrifically serious” arm injuries in the east London sword attack that claimed the life of a 14-year-old boy, the Metropolitan Police Commissioner has said.

Sir Mark Rowley told LBC the officer had undergone several hours of surgery on Tuesday and faces “a long journey of recovery” after nearly losing her hand.

He said: “The surgeon spent many, many hours basically putting her arm back together.”

A male officer also suffered serious hand injuries and is recovering in hospital.

The boy who died is understood to have been a pupil at Bancroft’s, the same school attended by Grace O’Malley-Kumar who was killed in Nottingham last summer as she tried to save her friend Barnaby Webber from a knife attacker.

The boy’s mother works at Holy Family Catholic School, which published a statement on its website addressed to parents and carers that said: “It is with great sadness that I share with you the news of the death of the child of one of our staff members.

“Mrs Anjorin’s son was taken from this life suddenly this morning on his way to school. Please keep Mrs Anjorin, her husband and their other children in your prayers.”

Sir Mark told the broadcaster: “People say officers run towards danger.

“What you’ve actually seen on some of the videos that are around social media and on news sites… you actually see what that really looks like.

“You’ve got officers running towards someone who’s waving a sword.”

The horror unfolded in Hainault on Tuesday morning when a man armed with a sword went on the rampage, killing the teenage boy and injuring two other members of the public as well as the two police officers.

Neighbours said the attacker first spoke to a woman, asking her to confirm his location, before she saw the weapon and fled. She tried to warn the teenage victim, said to be a Nigerian boy, but it was too late.

Speaking about the victim, Sir Mark said: “The first thing you have to say is for the parents involved, who’ve lost their 14-year-old, that is just horrific, and it’s everyone’s worst nightmare.

“I’m sure we’re all thinking about them.”

Terrified residents hid as the swordsman climbed over garden fences, before police managed to Taser and arrest him.

The 36-year-old suspect remains in hospital after being injured when he crashed his van into a house.

Chief Superintendent Stuart Bell, of the Metropolitan Police, said he did not believe it was a targeted attack, and it is not believed to be terror-related.

Dramatic footage obtained by the PA news agency captured the suspect being cornered and tasered by officers on a residential driveway.

The video shows officers shouting at the suspect, saying “Don’t move, don’t f****** move” after he is brought to the ground by three separate Taser discharges.

The words “Suspect contained” are eventually heard as a female officer pulls the sword away from the attacker.

A Buckingham Palace spokesman said the King’s “thoughts and prayers are with all those affected” by the “horrific” stabbings, adding: “In particular, the family of the young victim who has lost his life.”

Amid speculation about previous police contact with the suspect, Metropolitan Police Assistant Commissioner Louisa Rolfe said on Tuesday that “no trace of a prior incident” involving him had been found, but that the force will continue to make checks.

A neighbour from nearby Laing Close, who witnessed the attacks, told PA he could “not stop envisioning the boy’s face”.

James Fernando, 39, said the suspect had asked one of his neighbours to “take the telephone from him to tell whoever was on the phone his location”.

He told PA: “Within two seconds after that she’s realised something isn’t right, started running and he’s pulled a samurai sword from the back of his trousers.

“She’s shouted to the other neighbour – a Nigerian boy who was on his way to school.

“As he’s turned around, he’s struck him on the face… he was dead on the spot.

“It’s quite traumatising now. I can’t stop envisioning the boy’s face.”

Speaking about what he saw of the suspect, Mr Fernando said: “He was running around, still after the police officers came, with the sword in his hand, looking for victims.”

Another witness, who asked not to be named, told PA he heard shrieks and screams following the incident.

He said that from his window he saw a man dressed in yellow jumping over fences and heard someone shout “He’s got a massive knife”.

His words follow footage shared on social media of a man in the area dressed in a yellow hooded jumper brandishing a large knife in his right hand.

Other footage showed the suspect being chased by police as an officer is heard shouting “Lock your doors” when the sword-wielding man entered residential gardens.

Officers could be heard yelling “Come here”, “Come this way” and “Drop the sword” at the suspect, who could be seen climbing on top of an outbuilding and dropping into a garden.

Prime Minister Rishi Sunak described the incident as “shocking”, adding: “Such violence has no place on our streets”.

Footage seen by PA shows a man in a yellow jumper chasing after an ambulance while holding a sword as a body lies motionless on the ground.

The home security video shows an ambulance parked next to the body lying on the road in Laing Close before the ambulance quickly drives away from the scene and the man runs after it, shouting.

In another video clip, sent by an anonymous resident, a police car arrives before the man verbally confronts the police and shouts “Is there anybody here who believes in God?” while standing next to the motionless body.

A voice is heard shouting “Drop the sword” before a police officer approaches the man and sprays a substance in his direction before he retreats.