Thames Valley Police are looking for local man Jed Allen after the bodies of a man, woman and young girl were found dead in a house in Didcot, Oxfordshire.
Police found the bodies of a 44-year-old man, a 46-year-old woman and a six-year-old girl at a house in Vicarage Road after a call from a member of the public on Saturday night.
They were later named as Philip Howard, Janet Jordon and her daughter Derin Jordon. Police said they died of stab wounds.
Detectives say they want to speak to Jed Allen, a 21-year-old man related to the victims, who has a number of distinctive tattoos.
Oxford University parks have been closed at the request of the police, after reports that Allen used to be a groundskeeper at the world-famous university.
Pictures posted on Allen’s Instagram account show he has a tattoo of a spider on his left hand, a scorpion on his right and another animal tattoo on his chest.
Other photographs show Allen posing with knives.
Speaking at a press conference, Detective Superintendent Chris Ward from Thames Valley Police’s Major Crime Unit said: “He is described as being 6ft tall. He is of large build but distinctively, he has a tattoo on his left hand of a spider.
“It is very important that we locate him as quickly as we can.”
Mr Ward added that although Allen was not considered a danger to the wider community, the public should not approach him and contact police immediately.
He said all three victims – who had only been living at the address for around two months – were “related” to each other and to Allen.
The suspect is known to police and local to the area, Mr Ward said.
He added: “At this stage the families of the victims have been informed and they are being looked after by specialist, trained officers.”
No arrests have been made and it is not believed that any firearms were involved.
Officers received the tip-off at around 8.23pm and detectives are keen to hear from witnesses who may have been in the Vicarage Road area at the time.
Police will be carrying out a number of overt searches in the Didcot area and have asked anyone with information about the incident to contact them immediately on 101 quoting reference number 1370.