"We'd probably been going for about 45 minutes I suppose and then came down a hill and a girl was sort of sitting on a bike, waving for people to stop.
"Of course our group stopped and noticed the guy lying on the ground under a tree. We thought he was still alive, we thought he was warm, but it turned out once the ambulance got there that he was dead.
"I just watched the news again on TVOne and it just showed a picture of the guy they were looking for in relation to it and that is the guy, I'm sure of it, just that haircut and the greyish hair.''
Mr MacDonald said he didn't see the woman's body.
"I shot away on my bike and another of my friends was there and he waved me down to say that there was a dead woman in the trees, about 50 metres up the track.''
Jenni McDonald also saw the bodies.
She told 3 News the woman was not wearing pants and there was alcohol nearby.
Earlier today South and Mid Canterbury area commander Inspector Dave Gaskin refused to say how the man and woman died.
"I'm not going to comment on any possible injuries until we have finished our scene examination and have all the details so we can give you an accurate description,'' he told APNZ.
The pair were not thought to have been dead for long before the bodies were found.
News from the scene was filtering through slowly because the area was "extremely isolated'' and lacked cellphone or police radio coverage.
"We're just taking it very slowly and making sure we get it right,'' Mr Gaskin said.
The bodies have been flown to Christchurch for post-mortem examination.
Police are hoping to confirm the names of the dead by the morning, once next of kin have been contacted.
Mr Williams indicated the deaths probably occurred at the scene, but said officer are still looking for a vehicle of interest.
Earlier they appealed for sightings of a silver 1997 328i BMW saloon, with the registration ATT530, last seen parked at Mr Frandi's home about 11am on Saturday.
Police have set up a wide cordon around the scene.
Today, a single officer in a patrol car guarded the entry to the site at the foot of Pentland Hills Rd - a winding, country road surrounded by rugged, hilly farmland, and pine forestry.
The find was the subject of much speculation and rumour in Waimate.
One local man, who wished to remain anonymous, said several people he had spoken to walking down the main street had been talking about the incident.
"Some members of the community have been saying these sorts of stories give Waimate bad publicity,'' he said.