Two women were killed, and a man and a teenager were seriously injured in the stabbing Christmas day.
Detectives launched a murder investigation after being called to a report of a stabbing at a block of flats in Bletchley, Milton Keynesat 18:36 on Wednesday.
A 38-year-old woman and a 24-year-old woman died on the spot. A teenager and a man in his late twenties were taken to hospital with serious injuries, where they remain in a stable condition.
The dog was also injured and taken to the vet, but did not survive.
A 49-year-old man from Milton Keynes was arrested on suspicion of murder and attempted murder. He remains in police custody.
Forensic teams were spotted searching a house near the scene on Santa Cruz Avenue, as police confirmed they were not looking for anyone else in connection with the stabbing.
Senior Investigating Officer, Chief Inspector Stuart Brangwin, from Thames Valley Police’s Major Crime Squad, said: “Firstly I would like to express my deepest sympathies to the families of the women who have tragically died in this shocking incident.
“We have launched an investigation into a double murder, which may be of concern to the general public; however, we have made an arrest and are not looking for anyone else in connection with this incident and the parties are known to each other.
“Members of the public will see a heavy police presence in the area as our investigation unfolds. If you have any questions or concerns, please feel free to contact our staff and they will do their best to help.
“Anyone with information or footage that you believe could assist our investigation, please call us on 101, quoting reference number 43240622935.
“Alternatively, you can make a report online or contact the independent charity Crimestoppers on 0800 555 111.”
More to come on this breaking news…