Today the jury heard the boy, who cannot be named for legal reasons, tell police: "I had a vision. I had a funny feeling that Matt was going to come down the drive and visit us that day when Peter was [there]. And it came true."
Edmonds arrived at the house unannounced in his truck around 6pm that evening, having driven from Whanganui when the woman did not return his phonecalls that morning.
"I had a flash when Matt got there that someone was going to get hurt, mum's going to get hurt, and Peter's going to get smashed. It came true," the boy said.
The boys went into the house with Edmonds and Mr Bettink, but the boy said he whispered his fears to his brother on the way inside.
"I didn't feel good about this. I felt someone was going to to get hurt, [I whispered] 'just stay away from Matt and Peter' ... and he listened to me. And then this happened."
The boy described how initially it had been a calm meeting between the two men, while they waited for his mum to come home with dinner.
But he overheard Edmonds phone his mum and say, "I thought you loved me" - "and then he went 'eff off'".
When his mum got home "it all went wrong".
"Matt and Peter had a big argument. He [Edmonds] called mum a 'B'," he said in the interview.
Edmonds pushed the woman to the ground, injuring her chin, before he allegedly attacked Mr Bettink.
The boy's younger brother, then aged 7, witnessed the fight between the two men. His interview tape was also played to the jury today.
He described a loud argument, in which Edmonds verbally abused his mother.
"Matt was saying the 'F' word, and the 'B' word, and the 'S' word, like every bad word. And then Petter was trying to [say] 'cut it out'. Then he [Edmonds] was moving onto Petter.
"He was starting to punch him, and then Petter was getting smashed out, lots of times, that I couldn't even count because he was doing it too fast."
He added: He was punching him, here, here, and here," indicating his head, eye and jaw areas.
"He [Mr Bettink] was falling because he lost control. And when he fell on the concrete he was bleeding out of his head."
Edmonds "was punching because he didn't like that mum had a new boyfriend", the boy told police.
The two boys then rushed to Mr Bettink's aid as Edmonds drove off in his truck, and their mother rang emergency services.
"Petter was lying on the ground with a broken nose, a punched up mouth, one eye closed with the other eye partly open, just staying there," the older brother said.
He shouted to his younger brother to get some toilet roll from the bathroom, which they used in an attempt to clear away some of the blood and stem the bleeding from Mr Bettink's nose.
"There was piles of blood, everywhere."
The boy then attempted CPR, and also followed instructions from emergency services, by rolling Mr Bettink into the recovery position.
"The phone said put him on his side, he was going all purple, dark purple. I put him on his side, going slightly lighter purple.
"Then I pulled him on his back with a pillow on his head.
"Petter started breathing a little bit better."
Emergency services took over, but were unable to save Mr Bettink, who died at the scene.
The younger brother said the incident had made his mother "very sad", and he too felt "sad inside" because of what had happened.
The older boy told police he was "pretty disappointed" in Edmonds.
"And really angry, and upset."
He described Mr Bettink as "mum's good friend", and said: "Me and my grandma were hoping for them to be happy together and all that."
The trial, before Justice Geoffrey Venning, continues.
