Canterbury district commander Superintendent John Price said police received a phone call at 4.05am from an elderly man living at the house.
He told police he had used a firearm and was intending on doing self-harm.
Price said there was no further conversation after this, but the phone call continued and a loud noise was heard in the background.
A police negotiation team and armed offenders squad were called to the property immediately.
When officers entered, they found an elderly man and an woman dead on a bed, he said.
There were four firearms and about 100 bullets found at the scene.
Price said a homicide investigation is underway and there are 12 investigators on the case.
Authorities are not looking for anyone else in relation to the incident.
"This is an absolute tragedy. It is a reminder to us all we need to care for each other, care for our neighbours and care for our wider community.''
Price also revealed that he understood there had been regular medical assistance required at the address.
- Starnews.co.nz, NZ Herald
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
OR IF YOU NEED TO TALK TO SOMEONE ELSE:
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