Former constable Benjamin Peter McLean (48) found out on April 5 40-year-old Verity ''Bert'' McLean was leaving him for his best friend, Garry Duggan (48).
Less than three weeks later, the defendant shot the woman dead in the house she shared with her new partner, and attacked Mr Duggan when he arrived home from work.
Yesterday, in the High Court at Invercargill, McLean was sentenced by Justice Rachel Dunningham to life imprisonment with a minimum non-parole period of 17 years after pleading guilty to murder and attempted murder.
He was allowed to read a statement from the dock while fighting back tears.
''I will forever regret the pain and suffering I have caused my children,'' McLean said.
''The two most important adults in their lives are now gone.''
He finished the speech with reference to his dead wife.
''Bert was the love of my life and broke my heart, my soul,'' he said.
Mr Duggan said McLean continued to blame others for his heinous actions.
''There's no remorse, no guilt. He likes what he has done,'' he said.
''He's screwed over so many people ... and he doesn't care.''
Mr Duggan - who had been a close friend of the defendant for 15 years - said he and Mrs McLean never wanted to hurt anyone when they started seeing each other before Christmas last year.
''We knew there was something big missing in our lives and we knew the other person was the only person to make us whole,'' he told the court.
''My strongest feeling . . . is of guilt.
''I loved this woman and she loved me, she felt safe with me and I couldn't protect her from the evil of Ben McLean. It's a legacy I have to live with forever.
''He planned to kill Bert, he planned to kill me.
''If I'd been a physically weaker man, there would be no-one here to tell you what an evil bastard he really is.''
On Anzac Day, McLean arrived back at his Scott St home after taking two of his children to an aunt in Dunedin.
He had argued with Mrs McLean on the phone after she had broken into the property to pick up some belongings.
In response, McLean assembled a kit bag which made his murderous intentions clear. He packed a police-issue wooden baton, blue disposable rubber gloves, a small bottle of hand sanitiser, plastic handcuffs (the same type the armed offenders squad uses), strips of towel and a portable radio tuned to the Invercargill police channel.
Most significantly, he also took a cut-down .22 rifle with a silencer attached.
After binding and gagging Mrs McLean, he shot her once under the chin, then he lay in wait for Mr Duggan.
McLean shot him once in the chest and once in the arm but the victim hit back, grabbing the weapon from the defendant and smashing him over the head.
The brawl continued with McLean making use of the wooden baton but that, too, was wrestled from him.
''You were relentless in your attack on him,'' the judge said.
The violence only stopped when the pair became exhausted.
Soon after, McLean left the property on his bike, leaving his former friend on the driveway bleeding profusely with two bullets inside him.
One of those bullets is still there, beside Mr Duggan's spine; an operation to remove it considered too dangerous.
While hiding from police, McLean called his children and admitted the heinous acts.
Counsel Bill Dawkins said none of the history in the McLeans' relationship justified the violence but there was a context around it.
He said McLean's acts were not only sparked by his wife leaving him but another perceived betrayal five years earlier and the discovery that he was not the father of one of their children.
Mrs McLean's father, Bob Barber, said no-one saw it coming.
''I have known Ben McLean for over 23 years and I cannot comprehend how he could take Verity from us in such a cowardly, callous and brutal way,'' he said outside court.
''He said he had lost the love of his life, in court. He didn't lose her; he executed her. His only regret was getting caught and not finishing off what he set out to do.''
Mr Duggan looked ahead with sadness to the ''final injustice'' of McLean being released on parole but he had a final message for the woman he loved.
''You will never be forgotten, you will always be loved, until the end of time.''
Justice Dunningham said the defendant had been segregated from the general prison population since being on remand and would continue to be held in solitary confinement for up to 18 months.
