COVER STORY: Claire and Charlotte were gunned down by the person who should've loved them most.

The following contains details of violence and domestic abuse that may be distressing to some. For 24-hour support please call Lifeline on 13 11 14, or call the National Sexual Assault, Domestic and Family Violence Counselling Service on 1800 RESPECT.

Crack.

Crack.

A pause.

Crack.

Three gunshots tore through the calm morning air in Spalding, a small town in Lincolnshire England’s central east. It was just before 9am on July 19, 2016, and the local swimming pool carpark had become a crime scene. Three were dead: Claire Hart, 50, her husband of 25 years, Lance, and their 19-year-old daughter, Charlotte.

At first, confusion reigned; nearby schools were placed into lockdown, news helicopters circled, whipping up rumours of gang violence, even terrorism. But it soon became clear there was no rogue gunman, no immediate threat the local community. The perpetrator lay among dead, sprawled alongside those he was supposed to love the most.

A single-barrelled shotgun in hand, the 57-year-old father ambushed the women after their morning swim at the The Castle Leisure Centre. His shots, the final act in a decades-long campaign of abuse and total control.

As the crime unfolded that July morning, Claire and Lance’s eldest children where hundreds of kilometres from the horror; Ryan, then 25, working in the Netherlands, and 26-year-old Luke in Scotland.

Ryan had seen the headline first, ‘Three dead in shooting in Spalding’. He texted his mother and sister, “…Let me know you’re OK. Call me please.” No response. He called. No answer. Panic rising, he phoned his brother and each rang police. When Luke’s inquiry was returned, the voice on the other end of the line asked a question that jolted him into a new, terrifying surreality: “Is that Luke? Do you have anyone with you?”

As he recounts in their book, Operation Lighthouse, “A panic rose strongly within to mould the world back to how it should have been. But this world was no longer mine. Everything froze. As a small, lonely child, I stood in silence in the infinite darkness.”

***

As so many survivors of domestic abuse will attest, Lance’s abuse hadn’t been clear to Ryan and Luke growing up.

Their father had never been physically violent toward the family, and though they recognised his short fuse, they saw his verbal outbursts as a means of discipline, an expression of authority that they - as children - had no choice but to obey. They had never considered that a man might wish to isolate his family, to destroy their self-esteem, to subject them to servitude. Let alone to kill.

"We knew our father was bad, but we never really considered he could be a murderer," Ryan told Mamamia. "There was a lot of confusion around what happened and how we hadn't realised our father was dangerous. There was obviously a lot of guilt and regret about what we could have done and what life could have been if we'd made different decisions."

Just days prior to the murder, they had moved their mother and sister to a new rental home, a secret operation designed to liberate them from their misery. Their experience was a tragic illustration of research that shows how separation can be a particularly dangerous time for victims of domestic abuse. In Australia, for example, one third of the 152 domestic violence-linked homicides committed by men between 1 July 2010 and 30 June 2014 were against an ex, and more than half of those occurred within three months of separation.

"[Moving our mother and sister out] was mainly to give them a life. Living with our father stopped us from doing anything; our mother's life in particular was just consumed with serving him. She had no freedom at all. She was never able to go on days out or holidays with friends," Ryan said. "So we weren’t moving out in fear of our lives being taken by him, we were moving out because of the fear that our mother and sister might never get to live."

Abuse doesn’t always mean bruises and broken bones.

It wasn't until after their father's crime that the Hart brothers came to understand that abuse isn't always bruises and broken bones, that murder isn't always preceded by aggression and flying fists. The realisation came courtesy of poster they saw strung up at a police station just days after the shooting. It described the characteristics of coercive control; a pathological pattern of abusive behaviours designed to reduce the agency, resources and self-esteem of another person/people.

1. Isolation from friends/family and restricting an independent social life. 2. Monitoring activities and movements. 3. Creating and enforcing arbitrary rules. 4. Threatening reporting to the authorities. 5. Controlling finances. 6. Repeatedly belittling and criticising.

Police say deadly shooting near swimming pool in Spalding is not terror related https://t.co/OEJu0FqYJ7 pic.twitter.com/Nbto9qj1Jh

— ITV News (@itvnews) July 19, 2016

"We just hadn't realised the violent component of those behaviours. We'd been very materialistic about what violence was," Luke said. "We hadn't seen violence in the context of an assault upon our lives and our freedom; we didn't see it in that kind of abstract sense. But actually it showed that those who are willing to assault you on your basic values are willing to kill you."

That poster unlocked something in both men. It started unravelling their past, helping them to shake off the brainwashing they'd received from their father and recognise his methods of control.

How they moved house frequently away from established relationships; how he'd forbidden social media and restricted use of the internet; monitored phone records and call back numbers he didn't recognise; how he’d exclusively controlled the family’s finances; how he'd kick the family dog to punish his children; how he would purposefully cause their mother stress knowing it would exacerbate her Multiple Sclerosis symptoms.

The control had been so strategic and so systematic that, in a way, Ryan said, their mother's life had really been taken 25 years earlier - on her wedding day.

Helping others recognise those signs is why Luke and Ryan are speaking so openly about their father's behaviour now. They've spent the past two years training police and prosecutors in precisely that, and with their book they hope to spread the message about the different shades of domestic abuse. Especially those more difficult to detect.

As they write in Operation Lighthouse, "What appears to be a lack of visible abuse may be indicative of the very abuse suffered. A family that is always together may be one that is not permitted to be apart. A family which always seems to follow the rules could be one terrified of the consequences should they be broken. A family that struggles to leave an abusive father may have no resources to do so."

Their book was named for the random title stamped on the shooting's police file, but reflects Ryan and Luke's determination to shine a light on the darkest day of their lives and guide others to safety. And it's working. Several women have contacted them to say their message not only resonated but has likely saved their life.

“We have a moral imperative to [share our story] as much as possible, because if we can have that effect from just a few discrete events then we realised that if we can tell it more broadly hopefully women can not only realise their situation but they can actively challenge it,” Luke said. “It seemed like something that we couldn't back away from.”

This fuels their sense of purpose, but so does a desire to unpick the threads of toxic masculine ideology. The kind that demands superiority and control. The kind that leads men to kill. The kind that saw the media quote sources that described their murderous father as a “very, very nice guy”, and probe his backstory for something that might justify his (unjustifiable) crime.

“We realised it fundamentally comes down to the fact that men feel entitled to kill. That's why men continue to kill women and children, because they feel they can and because other people will eulogise them in the event they do,” Luke said.

At the root of the problem, they argue, is society’s understanding of what men and fathers are and their roles in families and communities.

“We're all to blame for what men have become, through every small action we take to reinforce those ideals,” Luke said. “Men are something they don't wish to be anymore but they don't know how to be something different.

"For men's sake, as well as everyone else's, we need to create a new 'man'. We're hoping to at least open that conversation up; it's a massive conversation, but one that really needs to be addressed.”

More personally, sharing their story is also a way to reclaim their narrative from their father. A man who left a 12-page murder note, one he’d been drafting for months - long before Claire and Charlotte moved out - in which he attempted to rationalise his crime: "You destroyed my life without giving me a chance," he wrote, according to local media. "Revenge is a dish served cold."

"Our father has left the note to try and control the narrative from the grave. I guess [Operation Lighthouse] is the note that was never left -  the victims' note," Luke said. "Our mum and sister's note, our note."

Though their grief is still Luke can now look at photographs of Charlotte and Claire without the pang of guilt and grief, the anger of what he's lost. He can see in their faces the times they had together, the love they shared, and just be thankful they had it at all.

"Everything that's happened, everything that our father had done was designed to ruin our lives. But the only thing he can't take away is our smile. As long as we can smile despite everything he's done, then he's lost. And I think that's the kind of thing our mother and sister would have wanted, it's the thing that we've realised we have to do," Luke said.

"People ask, 'Would you rather he was alive and got justice?' But I suppose it doesn't matter, really. We're glad he's dead. But it's irrelevant what happens to evil people. I think we just need to find our own justice, and the best justice we can hope for is a life worth living."