A court has heard how a young Taranaki man turned from a once "kind soul" into a self-confessed "monster" - ultimately taking the lives of his father and step-brother in a frenzied, early-morning attack.
Nathan Frost, 21, appeared in the High Court at New Plymouth this morning, having earlier admitted to murdering Stephen John Frost, 55, and Regan Frost-Lawn, 15, at the family's Hawera home.
The court heard how, in the early hours of January 18, Nathan Frost was heard to be distressed and crying in his bedroom, causing his father to check on him.
Nathan, who'd consumed a large amount of alcohol, then attacked him with a pipe wrench, which he used to strike him repeatedly about the head, jaw and arm as Stephen fell to the ground unconscious.
Nathan then unfolded a large hunting knife and stabbed him in the neck, severing Stephen's carotid and jugular veins and lacerating his wind pipe.
At this point, Regan confronted Nathan, telling his half-brother: "Get off him you mongrel".
After Regan called out to his 14-year-old sister Grace, who was outside in a sleep-out, warning her: "He's got a knife."
Nathan then began attacking him, stabbing him repeatedly around the back and shoulder area, as well as four times in the neck.
Next, Nathan moved outside to the sleep-out - but Grace had already fled and hid nearby, from where she phoned for help.
Police arrived soon after and arrested the 21-year-old at the scene.
In court today, members of Frost's family spoke of how they'd been left traumatised by his actions.
In a victim impact statement read to the court by prosecutor Justin Marinovich, step-mother Michelle Lawn told Frost there "not enough words or time to express how much you have caused".
She told her step-son that his acts had been carried out "purposely, violently and cruelly, with injuries that are indescribable".
"If not for her instincts to run, I'm sure without a doubt, you would have also taken the life of your 14-year-old sister Grace."
She said she's spent "countless nights awake" thinking of ways that she could have prevented Frost from hurting her son and daughter.
"You have taken the future of my son away. I am left with what ifs, and things I will not get to see.
"I will never see him grow into a man, have a life, get married, or become a father. You have stolen this promise.
"Grace is terrified of you and that you will get out of where you belong. We are scared of the dark and the constant thoughts of you."
In his statement, brother Jaydan told Frost: "I feel you have brought shame on the family and honestly I find it hard to even contemplate calling you my brother."
He said that, as a child, Frost had the "most caring soul".
"But as you grew up, you changed. You became a different person, selfish in the extreme, only ever thinking about yourself."
Jaydan said it pained him that their father – a Fonterra employee who was well regarded in the local community - wouldn't get to see him build a house, get married, or welcome his granddaughter into the family.
"You have not only taken away the only father in law to my partner... but you've also completely s**t on the way mum brought us up."
Stephen's sister, Alison Turner, told Frost he was a "pitiful, self-centred, nobody".
"A stronger person would have acknowledged they needed help. You chose not to."
Her brother, Grant Frost, told his nephew "there is no place on this planet for a disturbed soul like yours, who killed their own kind in cold blood".
"Your horrific actions have affected and changed our family forever... a family with which you will never be involved or a part of, ever again."
Ahead of sentencing, Marinovich told Justice Ellis that, while the killings may have been seen as opportunistic to some extent, there had been "significant planning and forethought" involved.
He noted how Frost had taken the wrench from an outside shed, purchased a knife, and had walked out to Grace's sleepout after murdering Stephen and Regan.
Defence counsel Paul Keegan however cautioned against speculation, pointing out that Frost hadn't been charged with attempted murder.
He described his client as a "young emotionally damaged man with rehabilitative prospects", and told the court how, at one point, he'd acknowledged that his actions were "disgusting" and that he'd "acted like a monster".
In sentencing, Justice Rebecca Ellis noted that Frost had harboured resentment toward his father over separating from his maternal mother, and had been left a "ticking time bomb" by his use of drugs and alcohol.
She said it was only through luck and quick thinking that his sister had escaped, and that Frost wasn't being sentenced for three murders.
"I have no doubt that Regan saved Grace's life that night."
Justice Ellis said she was satisfied a sentence of 20 years - two life sentences - was not manifestly unjust, given the circumstances of what she called "very brutal" offending.
"The pain you have caused to those left behind is unimaginable," she told Frost.
"As Grace put it this morning, they are stuck in a pitch-black room, under a rock, full of thoughts.
"In the end, though, it is clear that your family remains strong and fiercely loyal to each other. They will not let what you have done defeat or break them.
"They will stand together and, I think, they will survive."