The sons of a 'bullying' man who shot dead his wife and daughter after ambushing them outside a leisure centre have published a book following the tragedy.
Lance Hart, 57, wrote 'karma is a b***h' in a 12-page suicide document before killing his wife Claire, 50, and their 19-year-old daughter Charlotte with a sawn-off shotgun.
He then turned the gun on himself on July 19, 2016.
Following his death, his sons, Luke and Ryan, 26, told how they had endured a "lifetime of struggle" at the hands of their controlling father.
But determined to draw a positive outcome from the unimaginable tragedy, they have now penned 'Operation Lighthouse' to raise awareness of domestic abuse.
Speaking of its release, the pair said: "Two years after our father murdered our mother and sister, we have released our book to give a voice to our mother and sister and speak honestly about our experiences growing up and following the murders.
"1 in 4 women will suffer domestic abuse in their lifetime. We can all do something to change this, in fact by sharing this you could be saving someone’s life very close to you.
"Maybe neither of you see the abuse for what it is, maybe you never talk about it or maybe they feel terrified and alone and hide it; we hope that sharing our experience can go some way to changing that."
The brothers also opened up about their experiences of growing up with Hart and the circumstances surrounding the murders.
They hope it will highlight the patterns of behaviour in coercive control and its deadly consequences, and also improve public awareness on domestic abuse.
The book has a foreward written by Labour leader Jeremy Corbyn MP, who said: "In the words of the great Angela Davis, “I’m no longer accepting the things I cannot change, I’m changing the things I cannot accept”, and it is with this boldness that Luke and Ryan have used their own experience of domestic abuse to help others."
Claire had packed her bags and walked out on July 14, 2016, because she'd 'had enough' of her 'selfish' husband, who spent the next five days plotting murder.
As he ate a 'last supper' of paella and wine in his garden on the night before the shootings he wrote: 'Revenge is a dish best served cold'.
The killer also said his three children were 'conspiring' against him and would murder his estranged wife and only daughter to spite them and his surviving sons Ryan, 27, and Luke, 28.
In a message to his family he wrote: 'You completely destroyed my life without giving me a chance so I will destroy yours.'
He added: 'Karma is coming, Karma is a b***h, now you all lose'.
Hart then lay in wait for his wife and daughter outside the Castle Leisure Complex in Spalding, Lincs., shooting them both dead in the stomach.
An inquest into their deaths heard how police found a sick 12-page document Hart left which blamed his children for his actions.
Luke previously described his father as a "terrorist", and said: "He had nothing to live for other than killing us."
He added: "Someone like our father was a terrorist. He was planning to kill all of us three weeks before killing them.
"When it's your own father... the anger is inexplicable.
"It's so complicated and horrible and the media treated it like a one-off, but for us it was a culmination of a lifetime of struggle.
"He was vitriolic and a bully who would be verbally abusive and threaten us.
"In a way you feel pity and sympathy and feel weakness and think he needs help. When we tried to get him help, he'd refuse.
"He held traditional masculine beliefs and a lot of people think that is normal.
"He thought he owned us and saw us as protected by him but we were entirely oppressed by him."
Operation Lighthouse is now available on Amazon in hard copy and e-reader.
Sarah Norburn, the domestic abuse coordinator for Lincolnshire Police, said: "Luke and Ryan are shining a light on domestic abuse, illuminating a world of suffering, often hidden or silenced.
"Coercive control is designed to isolate and silence victims - it is created by invisible chains.
"Luke and Ryan are truly inspiring, bravely telling their story - in response all of us must engage in honest and open public conversation about domestic abuse."