Nikki Guy said she was trying to look after her mother when she heard Mr Berry say Scott had been stabbed - and Macdonald twice declared, "No, he was shot."
She listened to their exchange and remembered it because she wondered how close Macdonald had got to the body to be able to acquire that information.
"I remember thinking, 'How did Ewen know Scott had been shot, when he was down at the cordon?' and because I thought he was at the cordon, how close did he get to see Scott, and I thought that David, being first on the scene, would have had a closer look."
Nine months later, Macdonald, 32, was charged with murdering Mr Guy. He has pleaded not guilty.
The Crown alleges that under the cover of darkness, he gunned down Mr Guy, who was on his way to the milking shed, because he was jealous of him and feared losing his place on the family farm.
The way Macdonald described the injury is an important part of the Crown's case - the allegation is he could only say with certainty Mr Guy was shot if he was the one who killed him, because it appeared to others that Scott's throat had been cut and he couldn't have got close enough to the body to know otherwise.
The Crown says it was only when police found bullet fragments in Mr Guy's throat that his cause of death became known.
The trial has previously heard different statements from others who arrived at the Aorangi Rd scene about whether they believed Mr Guy had been shot or had his throat cut.
Scott's father, Bryan Guy, has given evidence that he doesn't know how the idea his son had been shot got into his head. But yesterday Nikki Guy said she was adamant it was Macdonald who had said that.
While Macdonald was standing to the side of the road crying, she heard him say: "It's not fair, it's not fair, we had so many plans."
She believed he was referring to the plans for the farm that had been discussed at a recent conference both men attended in Southland.
She said the phone call from her mother had left her in "shock and disbelief".
"It didn't enter my head that he'd been killed ... I thought he may have died in his sleep or some kind of natural causes."
She then went to Macdonald's home, where she broke the news to his wife, Anna - her sister - who had "no idea" what had happened.
Crown prosecutor Ben Vanderkolk asked Ms Guy if it was possible Mrs Macdonald knew of her brother's death before then.
Ms Guy said her sister definitely did not know and repeatedly said, "You're joking," when she was told.
Under questioning by Macdonald's lawyer, Greg King, Ms Guy said she didn't tell police about what the defendant had said at the cordon until four days later, when they asked her more detailed questions.
She agreed with Mr King that Macdonald had been upset and hugged her and behaved in a "way I would expect".
Earlier, Bryan Guy told the court of the disturbing 22-second phone call he received from Macdonald who told him something had happened to Scott.
Macdonald did not say anything about Scott being shot or having his throat cut, although Mr Guy was sure he used the words "his face", leading him to think Scott must have had an accident with farm machinery.
It wasn't until after Macdonald was arrested that he thought more about the words - and they bothered him.
"After I knew Scotty had been murdered, it was those two words that I wondered, 'What did you mean by that?' Those words bothered me because I hadn't seen Scott close up ... and I wondered whether Ewen had seen him close up to make those comments, and when it was he had seen him."
Macdonald's arrest came as a huge shock, Mr Guy said. "I didn't want to think Ewen was involved and did not want to think of any of our family being involved in it."
SCOTT GUY'S WIFE TO GIVE EVIDENCE
Scott Guy's wife will this morning give evidence for the first time at the trial of her brother-in-law Ewen Macdonald.
Kylee Guy is one of a number of prosecution witnesses called this week in the High Court at Wellington to talk about the events of July 8, 2010, the day her husband died.
Also expected to give evidence today is Macdonald's wife and Mr Guy's sister, Anna Macdonald.
Macdonald, 32, has denied murdering Mr Guy.
He has sat in the dock with his head bowed, taking notes for much of the time since his trial began on Tuesday.
Both Anna and Kylee - as well as Mr Guy's father Bryan, mother Joanne, and sister Nikki - are to give evidence on aspects of the Crown case more than once during the trial before Justice Simon France and a jury of 11.
- With APNZ
