Hawe wrote he "enjoyed" killing his wife and three kids

Extracts from the 2016 letter are included in a book written by Clodagh’s younger sister, Jacqueline Connolly.

Hawe, a deputy school principal, killed his school teacher wife Clodagh and their sons Liam, 13, Niall, 11, and six-year-old Ryan at their home near Ballyjamesduff, Co. Cavan, in the early hours of the day he was due to return to work after the school holidays.

Ms Connolly does not publish the full "murder letter| in her new book "Deadly Silence", due to it being "almost wholly a list of self-absorbed, egotistical excuses and lies for why he decided it was best to murder his family".

But she does include the chilling words where Hawe appears to admit to having enjoyed his grotesque crimes.

He wrote on the blood-stained pages: "I think there was some sort of psychosis that made me enjoy that, yet in the next moment, I was the complete opposite. I’m sorry for how I murdered them all, but I simply had no other way."

Ms Connolly speculates the word "psychosis" was chosen "to spoonfeed the forensic psychologists with the suggestion that he had lost his mind" – but notes that that notion is "contradicted by the detailed list of instructions he wrote on a separate leaf".

 She wrote: "He was still trying to control everything from beyond the grave."

The bereaved sister and aunt reveal it took 16 months before she and her mother, Mary, were able to see the letter, being repeatedly told it was evidence despite there being no trial.

Coffins of Clodagh and her sons at their funeral in Cavan.

Their solicitor, astonished to learn they had not seen it despite it being addressed to them, was eventually able to provide them with a copy. In the almost 1,000-word letter, in which Hawe refers to "I" or "me" 118 times, the killer said he had previously considered taking his own life only.

But he concluded that "Clodagh and the boys would never be able to live their hopes and dreams if I had killed myself". He wrote: "I know I would only be sentencing Clodagh to a life of misery."

The letter contains cryptic references to something that would "blow up" when he returned to school, possibly related to Hawe’s addiction to pornography, which he had been receiving counselling for. Ms Connolly shares a passage from the letter she believes was designed to pre-empt the discovery of "sleaze" on his phone and computer.

"Sometimes recently, when converting videos on ClipConverter, the odd dodgy website would pop up," Hawe wrote.

"I wasn’t looking for this to happen, and they were always blocked by the filter. I even looked at porn in the last few days on my phone, but I knew I had cracked up and it helped me forget."

Ms Connolly wrote: "His letter suggested everything I suspected. That he was avoiding the consequences of something he had done at work."

Clodagh had told her mother she threatened to leave Hawe over his issues with pornography. "He feared Clodagh was about to hear something that would prompt her to leave him for good. Had that fear triggered the murder spree?"

Ms Connolly never found out what, if anything, had happened at school. She initially assumed the letter was written in the kitchen, where it was found alongside folders containing the couple’s financial details.

But investigators later confirmed Hawe had written it on the coffee table, "sitting on the couch beside Clodagh’s bloodied remains".

Speaking on RTÉ Radio One yesterday, Ms Connolly said she could not ignore the fact that he used the word "enjoy" in his letter.

"We were told not to look at it that way," she said.

"But I suppose in recent times, when I’ve been writing the book, I’ve had to go back to that letter, and I’ve read that part, and I don’t see it any other way other than he enjoyed what he did.

"How do you make sense of such dark thoughts? You can’t. And I wouldn’t encourage anybody to go there. I don’t go there. I don’t think about what he said, because the letter was full of lies."

* This article was originally published on Extra.ie.