Police believe one of the bodies discovered at a property in Taharoa on Friday night was that of Ross Bremner, who has been on the run since allegedly stabbing his parents on Tuesday.
Three bodies were found by a friend of the couple just after 7pm. A silver Holden Vectra linked to Mr Bremner was also found there.
It is believed that the couple may not have known Mr Bremner.
"While formal identification is yet to take place, we believe one of the bodies is that of Ross Bremner," Acting Supt Naila Hassan of Waikato police said on Saturday.
"Police initially thought the victims were related to Ross Bremner. It has now been established they are not related at all, and we don't know how they knew Ross Bremner.
"It is possible that they did not know him at all."
An initial scene examination has suggested the bodies were there for "several days" before being found.
"We do not know why Ross Bremner has travelled to this location," says Supt Hassan.
Detectives are working to build a full timeline of the events that have occurred since Tuesday night.
Police have been searching for the 34-year-old since Tuesday's stabbing, which left Mr Bremner's mother dead and his father critically wounded.
Mr Bremner has been treated for mental health and drug addiction issues in the past.
The identities of the elderly couple, one of whom is believed to have recently celebrated his 80th birthday, will be released later today.
"The scene is very rural and is spread across a large area. Our detectives and forensic expects will be there for some time trying to build a picture of exactly what happened there."
Police say very few sightings of the silver Holden Vectra have been reported, and they are hoping to hear from anyone who has seen it since Tuesday night.
They say there is no ongoing risk to the public.
Anyone with information has been urged to call police on (07) 858 6200.