The body of a three-year-old boy was found at a home in London after police smashed down a front door.
Detectives said the remains were found with the bodies of a woman and a man who were also pronounced dead at the scene in Brentford.
Police raided the property in Claypods Lane at 12.50am following "concerns for the welfare of the occupants".
Cops found the bodies of three people inside, including a three-year-old boy, with a neighbour saying police told him the tragedy involved a family.
A spokesman for the Metropolitan Police said the body of a woman in her 30s and a man in his 40s was found suffering stab wounds.
The man was pronounced dead at the scene by the ambulance service.
A spokesman for the Met said: "Inside the address, officers discovered the bodies of a woman, believed to be aged in her 30s, and a boy, believed to be aged three-years-old.
"A man, believed aged in his 40s, was found suffering stab injuries. London Ambulance Service attended but he was pronounced dead at the scene.
"It is thought all three people were known to each other.
"Enquiries are underway to inform all next of kin.
"Post mortem examinations will be scheduled for all three people in due course."
Neighbours in the "nice area" have been left shocked by the tragedy.
One resident, who did not want to be named, said the police told him the tragedy involved a family.
The 29-year-old, who has lived in the building for a couple of years, said he did not know them but described the news as shocking.
He said: "It's definitely shocking and to just find out through police knocking on your door.
"They just said that a family had been found and wanted to check if we knew them or not."
He added: "This kind of news is not something you expect, it's a very quiet and peaceful area."
Sheri Diba, who has lived lived in the building for seven years, said: "I could not imagine someone is dead in this building. It's a very nice area, very nice building, I never had any problem.
"I'm really shocked."
Detectives from the Specialist Crime Command are investigating but it is understood they are not looking for anybody else with this incident.
"Enquiries into the circumstances continue," the spokesman added.
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