Anna Macdonald broke the news in prison to her husband, Ewen, that their marriage was over - and several months into a new relationship, according to a magazine article.
In an exclusive interview with North & South magazine, Ewen's parents Kerry and Marlene Macdonald describe their "harrowing" 15 months - from the time their son was charged with Scott Guy's murder to their relief on hearing the not guilty verdict.
Despite the verdict, the magazine cover describes Ewen Macdonald as having "lost everything". The Herald revealed earlier this month that the couple's marriage had ended.
Kerry Macdonald told North & South they visited Ewen in Manawatu Prison on many occasions, but the toughest time was when the marriage ended.
Anna broke the news to Ewen after Ewen's parents became aware she had been in a new relationship for several months.
"I told Anna, 'Visiting's for an hour; you go in first and then we'll go in afterwards and pick up the pieces'," Kerry Macdonald told North & South.
The 12-page article covers his reaction as well as how Anna reacted to the court verdict. Ewen and Anna Macdonald had known each other since they were teenagers and have four young children together.
Macdonald was charged with the murder in April 2011, nine months after Mr Guy was shot dead.
Scott Guy was Macdonald's best man and the pair were business partners on the family farm in rural Feilding. In an earlier statement, the Macdonalds told of being "totally at peace" with the knowledge their son was not Mr Guy's killer.
"After talking to Ewen at every prison visit possible and hundreds of phone conversations we are no longer 'confused and bewildered' but rather totally at peace with the knowledge we at least have his truth."
They had received enormous support from family, friends and colleagues since the arrest.
The Guy family have not publicly commented since the end of the trial when Bryan Guy read a statement to media on the courthouse steps.
There, he told of the family's desire to "close this chapter" of their public lives and reflect away from the public glare and "rebuild our lives".
Kylee Guy, in a separate statement, said the end of his trial was not the "final chapter".
"We are not going to give up. We will do everything we can so that [Scott] can finally rest in peace."
Macdonald is still in prison awaiting sentence on the arson, theft and vandalism charges he admitted at the time of his arrest for the murder.
Three other charges he has admitted are suppressed until his next court appearance on July 31.