Widow Kylee Guy has spoken out on the eve of the 10th anniversary of her husband's death, saying she knows who killed him.
And, in an exclusive interview with the Sunday programme she said the killer is still out there and she has just one message for that person.
"You are a coward. If you can live with yourself for doing this - taking a father away from his children, who was a good man - you are a coward."
Dairy farmer Scott Guy was only 31 when he was gunned down at the end of his driveway near Feilding on July 8, 2010.
He and Kylee had a young son, Hunter, and Kylee was heavily pregnant with their second son, Drover.
In the Sunday interview she described lying in bed with Hunter when she heard a noise and saw a truck at the end of the driveway.
When she went outside she was confronted by a police officer who told her, with tears in his eyes, that she needed to go inside.
She said she couldn't believe it for the first five days.
"I just kept thinking this is not real. I just couldn't handle it."
Ten years on, Kylee says she's not the same person.
When asked what kind of father Scott was, she said: "Over the top, just obsessed with Hunter".
"He just loved him to bits. He was an amazing dad."
Kylee told the programme she was no longer the "happy smiley Kylee" she once was.
"It's always in the back of your head, it's always consuming you. It would make it so much easier if it was all over and justice was done for him."
She says she was terrified after his murder and left wondering who could have done it and why.
But she had to keep going for her son.
She pleaded with anyone who knew anything to "do the right thing".
"If I had a million dollars I'd put it out there as a reward."
She said a young man was taken in "a horrible, horrible way".
"At the end of the day, nothing has been done. The killer is still out there."
In 2015, it was revealed a private investigation - launched by Kylee - had ended because of a lack of cash.
The Sensible Sentencing Trust, working on behalf of Kylee, had also approached four private investigators in a bid to find the killer and bring them to justice.
A member of the PI team, Mike Crawford, revealed in 2015 that the hunt had been dropped. "The investigation has basically stopped. It's finished," he said.
Former trust spokeswoman Ruth Money confirmed at the time that a lack of funds had curtailed the bid.
"Sadly, they've [PIs] stopped because there's no more funding," Money said. "The family can only spend so much."
Money told the Sunday programme that "fresh lines of inquiry were identified and handed to police" after the investigation.
"Without a doubt, there is compelling evidence that the police haven't investigated, and should," she said.
Asked why police had not pursued the leads, she said: "It could be resourcing, it could be a risk of reputation. I don't care. Kylee doesn't care. This is about justice for Scott. It needs to be handed to a completely new police team, and someone needs to be held accountable."
Kylee and Scott's sons Hunter and Drover are now aged 12 and 9, and Kylee has another son, Husky, now 4, with her new partner Kent Martin. Kylee said that when Hunter started school, another child said, "I saw your dad bleeding on the front page of the newspaper".
"It's those things I was trying to protect my children from," she told Sunday.
"All I can do is try to stay positive, surround them with as much love as you can, and lots of cuddles."
Scott Guy's parents spoke to the Weekend Herald last month in the lead-up to the anniversary, saying they thought about him every day.
"You can say it's 10 years since Scott was killed but it's actually 3653 days on his anniversary and every one of those days we think of Scott," Bryan Guy told the Weekend Herald.
"If we dwell on why or what if, it destroys you. Building resilience is where our focus is with our children and grandchildren - showing them the choices we make and how we react, they watch us all the time, let alone what we say.
"We want to be a good example to them and help them build strong relationships - to help them cope with life and the things that get thrown up. We live for helping our kids."
Sister Anna Guy said part of her was missing.
"It feels like Scott was here just yesterday but then other times it feels like it's been forever. I find it difficult when I see what Scott is missing out on but I am thankful for the time spent with Hunter and Drover. Being with them feels like you are close to Scott," she said.
Anna Guy's ex-husband, Ewen Macdonald, was charged with the murder but was acquitted.
Scott was the second eldest of four children — him, Nikki, Anna, and Callum.
After working on several farms and a short stint studying for a diploma in agriculture at Massey University in Palmerston North, he left for Australia to work on a farm. There he mustered cattle on horseback, fulfilling his dream of being a cowboy.
He returned to the family farm Bryerburn in 2003 and was put in charge of the crops and calf-rearing while Macdonald managed the dairy side. Superficially the working arrangement seemed fair and equitable but Guy's death later revealed tension and rivalry between the pair.
Guy met 18-year-old Kylee Bullock, who was training to be an early childhood teacher, at a Havelock North pub after a rodeo.
The pair fell in love and married in 2005.