Two brothers whose father shot dead their mother and sister have described him as a "terrorist".
Lance Hart, 57, killed his wife Claire, 50, and daughter Charlotte, 19, outside a swimming pool in Spalding last July.
His sons, Luke and Ryan, said they had endured a "lifetime of struggle" with his controlling behaviour.
"He had nothing to live for other than killing us," Luke, 27, told the Victoria Derbyshire programme.
The murders happened days after Mrs Hart had left the family home following a breakdown in the couple's marriage.
Hart shot the pair with a single-barrel shotgun in a swimming pool car park before turning the weapon on himself.
Luke said it was his father's final act to ensure the family could not live without him. He had left a 12-page suicide note saying "revenge is a dish served cold".
"It's pure evil, he hated us. He had the mentality of a terrorist, he was willing to kill himself to achieve what he achieved. Someone who's that fundamental, you can't stop. That's what makes our case so difficult to comprehend, we weren't safe whatever we did, if we had stayed he was planning to kill us there," he said.
"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."
The brothers said he controlled the household by restricting money and isolating their mother from support networks.
Luke said it was only in retrospect they can understand his subtle behaviours were about power.
"The thing that makes it really dangerous, he was always very self-escalating in his behaviour, as his final actions proved. He was incredibly self-destructive and for us it was always a matter of shaping around him - we had to give in.
"So we became really blind to it in the end, until we got to the point when he had mum's keys and documents and passport in a safe and we had no financial ability to do anything."
The brothers said their mother had been keeping a diary of everything his father had said and done, but "as there were no bruises" they never felt it was something they could take to the police.
Ryan, 26, said: "That's why we were so blind to our situation as we were looking out for physical violence. We didn't realise the danger of our situation. Physical violence is not the only sign of domestic abuse - quite often there is none."
The boys, who had worked hard to give their mother and sister a better life, had moved her out of the house so "she would be safer" while the couple's divorce went through.
At the time of the killings, some reports quoted neighbours who described Hart as a "very, very nice guy" who had struggled to deal with the breakdown of his marriage.
Ryan said: "Many tried to justify it as an act of love. I've since seen it's not unique to our situation. Love is one word which would not fit. It detracts from the seriousness of domestic abuse and almost sympathises with the abuser.
"When emotional abuse is talked about the onus is on the victims to escape or put up with it. There is no other form of murder where victims are blamed."
Watch the Victoria Derbyshire programme on weekdays between 09:00 and 11:00 BST on BBC Two and the BBC News Channel.