Two adults and two children who are believed to be from the same family have been found dead at a house.
The bodies of the four people and a pet dog were found at a property in Duffield Lane, Woodmancote, near Chichester in West Sussex, on Sunday.
Police have begun a murder inquiry, but said it was thought to be an "isolated incident contained to one property".
Sussex Police said detectives were not currently "seeking anyone else in connection with the incident".
"Our thoughts are with the family at this incredibly difficult and challenging time," Ch Supt Jerry Westerman said.
Officers remained at the scene on Monday night and Ch Supt Westerman said: "Local residents can expect to see an increased police presence in the area as our enquiries continue."