A woman was found beheaded in a garden at a home on Nightingale Road in Edmonton, north London, on Thursday, the Press Association reported.
Detectives involved in the case stated that there is no suggestion that the killing had any terrorist motive. A 25-year-old man has been arrested and is in custody.
Surrounding streets have been closed, but there is no suggestion of any ongoing threat to the public at the scene.
Eyewitnesses told the Daily Mail that they saw a man killing cats in the area before the incident was discovered, and police have confirmed that a man with a machete was seen there around lunchtime.
Police have identified the victim as 82-year-old Palmira Silva.
Sky News is reporting that other potential victims escaped from the scene, and that it appeared to be a random attack.
A man commented that he was "dragged" from his home by police warning him of a "dangerous man" on the loose.
Edmonton is a residential suburb in north London.
People there have been tweeting about the incident.
An aerial shot of the scene was shared on Twitter:
Here are some photos of the scene on Nightingale Road.
Forensics officers were at the scene.
According to several other reporters, this is the second fatal stabbing in the area today.
Commander sergeant Simon Letchford gave a statement to the press describing how the suspect was arrested.
He described a struggle in which several windows were smashed and the suspect was cornered in a house – not thought to be that of the suspect – and overpowered by officers.
One firearms officer suffered a suspected broken wrist, while the suspect is being treated in a nearby hospital for cuts and bruises. Letchford told waiting reporters that the original call to police took place after residents heard someone attacking an animal, possibly a cat or a dog.
Letchford praised the actions of the police officers on the scene.
He said that they put their lives on the line in what was a "fast-moving and difficult situation." He said the motive of the attack is still unknown, but that police do not believe it to be terror-related. He added: "These kind of events are very unusual."
Letchford confirmed that the suspect is currently in hospital and that uniform officers are conducting house-to-house inquiries.
The London Evening Standard on Friday morning reported the suspected killer has been named locally as Nicholas Salvadore, nicknamed Fat Nick. Locals reportedly said he was both a Muslim convert and an aspiring cage fighter.
Metropolitan Police on Friday released this image of Silva, who was born in Italy and had for 30 years worked in a local cafe with her son, Tony, it emerged.
Rossalyn Warren is a senior reporter for BuzzFeed News and is based in London.
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