A 95-year-old man who is believed to suffer from dementia has been arrested on suspicion of murder over the death of his female carer.
Two ambulance crews arrived at his first-floor flat in north London, on Thursday morning after a neighbour heard a scream at around 4am.
A 61-year-old woman was taken to hospital with head injuries but died just before 11am on Friday morning.
Scotland Yard has launched a murder probe after the altercation in Islington.
Detectives believe she was injured in the flat, where she was working as a carer. She is understood to have been an employee of a care agency commissioned by Islington Council, the Press Association reports.
The pensioner, who neighbours said was frail and uses a walking stick, was taken to hospital as a precaution after being arrested on suspicion of murder.
Police said he will remain there until he can be transferred to a location where his "complex health and care needs" can be addressed.
He is on bail as enquiries continue.
A neighbour who has been living in the 95-year-old's block of flats in Holloway for 10 years said he was rarely seen outside his home since he and his wife fell ill.
The woman, who did not want to be named, said another neighbour told her of hearing a scream in the early hours of Thursday morning.
She said the elderly man would normally have a carer looking after him and he was occasionally visited by family members.
"It's a surprise. They are a very good family," she said.
"I don't know what's happened. I was coming home from work and saw police upstairs.
"Another neighbour heard a scream at about 4am, but I didn't."
Councillor Richard Watts, leader of Islington Council, said: "We are devastated to hear of the death of a carer in Islington.
"Our thoughts are with her family and friends at this desperately sad time."
The woman's next of kin have been informed and a post-mortem examination will take place in due course, the Metropolitan police said in a statement.
A spokesman for the Met Police said: "A murder investigation has been launched after a woman died from head injuries following an incident in Islington.
"Police were called at approximately 7.10am on Thursday, May 24 to a north London hospital where a 61-year-old woman was admitted suffering from head injuries.
"She died in hospital at 10.57am on Friday, May 25."
He added: "Detectives from the CID based at the Central North Command Unit investigate.
"Officers are not seeking any other persons in connection with this investigation."
Anyone with information relating to this incident is requested to call police on 101. You can also contact Crimestoppers anonymously on 0800 555 111.