A 45-year-old Polish engineer has been found dead at his family home near Norwich with two young girls and a 36-year-old woman.
The injured bodies of Bartlomiej Kuczynski and what police believe to be three family members were discovered in Costessey on Friday morning.
Mr Kuczynski is understood to have lived in the semi-detached house with his wife, Nanthaka, and two children.
An engineering website run by him shows that he has worked in England for the past 20 years, and graduated from Wroclaw University of Technology.
The identity of the 36-year-old woman and children remains unknown. Detectives said she “was visiting and didn’t live at the property”.
Neighbours said Mrs Kulzynski’s sister had been staying at the house in recent weeks to help care for her brother-in-law. One said Mrs Kulzynski had not been seen at the house for several months.
A mother living near the scene, who asked not to be named, said: “We don’t know what happened. It is just devastating.
“The fact that children are dead makes it even worse. I can’t imagine what has gone on. I used to exchange neighbourly smiles with the family who lived there.”
Another neighbour, who also asked not to be named, said Mr Kulzynski had been reported missing around a month ago, shortly before Christmas. Police confirmed officers attended the property on Dec 14 last year in relation to a missing person enquiry.
The neighbour added: “There were five or six police cars outside their house. People were looking for him and then another neighbour found him walking up the hill round the corner.
“The sister-in-law then came round to help look after him. I think he had mental health issues at the time he went missing. People were talking about how he was not well.
“They were a very quiet couple and did not seem to speak to other people. It is just awful that kids are involved. The first I knew about something happening was when police knocked on my door this morning and asked if we had heard anything.”
Land Registry records confirm that Mr Kuczynski bought his home for £218,995 in December 2016.
Detective Chief Inspector Chris Burgess, of the Norfolk and Suffolk major investigation team, said: “We can confirm all four were found with injuries and post-mortem examinations will be held in due course to establish cause of death.
“We do believe they were all family members at this time. Officers are expected to remain at the scene for some time.
“We are still working to understand the full circumstances that led to the deaths of these people. However, at this time we believe this to be an isolated incident.
“I recognise the shock and upset this incident will cause in the local community, and we will have increased patrols in the area across the weekend. I would urge anyone with any concerns to speak to these officers.
“I’m aware there’s a lot of public interest in this investigation and speculation as to who is involved on social media, including the names of those who have died.
“The man and two children lived at the address, but the woman involved was visiting and didn’t live at the property. Next of kin have been informed and we are supporting them.
“We’re also aware of commentary on social media about a knife discovered in a wooded area near to the address. However, at this time we’re satisfied it’s not connected to this incident.”
01:35 PM GMT
Detective Chief Inspector Chris Burgess, from the Norfolk and Suffolk major investigation team, said: “Our investigation is in the very early stages and this is clearly a very distressing and tragic incident.
“While we’re following a number of lines of inquiry, at this time we believe this is an isolated incident.
“I understand that news of this incident will be shocking to the local community and as soon as we can we will release more information.”