Staff and residents at the housing trust where a man in his late 60s was allegedly assaulted this morning are devastated.
The incident occurred at the Dwell Housing Trust house on Mahora Street in the Wellington suburb of Kilbirnie about 9.50am.
Detective Senior Sergeant Warwick McKee said the victim was taken to Wellington Hospital in a critical condition.
Another resident was arrested and was being interviewed by police.
A Wellington Hospital spokeswoman said the man, who is in his late 60s, was still very unwell and was being treated.
Dwell chief executive Alison Cadman said most of the residents in the house had mental health issues.
"For us, our tenants' safety and wellbeing is our first concern so the fact that someone has been hurt in their home is extremely upsetting.
"This is a house that's been providing much-needed support and home to people in need for over 30 years, and this is the first incident we've ever had like this."
Ms Cadman said the trust had been working with the district health board to provide additional support to the remaining residents.
She did not know if all the remaining residents would be able to return to the house tonight.
"Our concern primarily now is for the residents who live there and their wellbeing."
It was a distressing and upsetting time for everyone involved, she said.
Mr McKee said police were making inquiries and speaking to a number of people.
"Police would like to hear from any person who may have seen a male person walking along Mahora Street, with no shirt on, heading towards the Coutts Street area, at around 9.50am this morning," he said.