Whenever I filed copy on the Ana Kriégel murder trial, I experienced a strange feeling, one I’d never had during the hundreds of other criminal cases I’d covered. It was guilt. There’s no other word for it. Every article felt like an intrusion into Ana’s privacy and into her parents’ unimaginable grief.

I got the same feeling every time I saw the 14-year-old’s photograph in the papers, whether it was the one of her smiling in science class or the one of her modelling in a fashion show to raise money for charity.

I fancy myself as a hard-nosed hack, who reports the facts as he finds them and to hell with emotions. But this time I couldn’t shake the feeling that none of us should have been in that courtroom, sitting a few metres from Ana’s mother and father as they listened to witnesses describe, in excruciating detail, what likely happened in their daughter’s final, terror-filled moments at the hands of two 13-year-old boys. I couldn’t shake the feeling that I shouldn’t be watching videos of one of the Ana’s killers describe her as a “weirdo” who dressed in “slutty clothes”.

I had an answer prepared for anyone who questioned me about the morality of reporting the trial in such detail. The press have a constitutional right, and a moral duty, to report what happens in the courts, I’d respond from my high horse. And that counted double when dealing with such an extreme case. Society needs to learn why two seemingly normal boys would lure an affable girl from her family so she could be beaten to death in a derelict farmhouse.

The case concluded last Tuesday, 18 months after Ana’s body was found by gardaí in the house. The teen known as Boy A, who beat her to death and violently sexually assaulted her, was sentenced to life, a term that would be reviewed in 12 years. Boy B, who lured Ana to the scene, was jailed for 15 years with a review after eight.

That evening, I sat in the corner of a pub, an untouched pint in front of me. The last article had been filed and my newsdesk had finally stopped ringing me. For the first time in what seemed like an eternity, I finally had a chance to think and I thought that my justification for covering the trial now sounded very hollow. Because, despite a massive police investigation, an eight-week trial, a stack of psychological reports into the boys and acres of press coverage, we still had no idea why two boys decided to commit murder and why they chose Ana.

Ana’s parents, Patric and Geraldine Kriégel, outside Dublin’s central criminal court after the two boys were sentenced for her murder. Photograph: Niall Carson/PA

It was a brutal case, one which at times seemed to traumatise the entire country. Murders like this happen, but not in Ireland and certainly not in a quiet suburban community on the border of Dublin and Kildare, a place where, in the words of Ana’s mother, Geraldine, “the only sounds in the morning are the doves cooing”.

The trial and subsequent assessments of Boys A and B did highlight several issues that might explain Ana’s murder, some more plausible than others.

Did bullying lead to Ana’s death? We know she was savagely bullied, particularly online. Other children sent her abusive messages and comments under the YouTube videos Ana loved to make told her to “go die”. But there is little evidence that the boys bullied Ana or even had much interaction with her. Of course, it’s possible they saw how other children treated her and thought that her vulnerability made her the perfect victim.

What about the content consumed by the boys? Both liked violent video games, but then so do most teenage boys. Boy A also liked horror movies but there is no evidence these were a motivating factor.

Perhaps less easy to discount is the pornography consumed by Boy A, including material depicting violence against women. Gardaí found thousands of images on his various devices, as well as internet searches for “child porn” and “horse porn”. But the psychological assessments stated that he had a normal view of sexual matters, a fact scarcely believable given the nature of the attack. Ana was naked when found, her ripped clothes scattered around the room.

In the absence of external factors, it’s tempting to label one or both boys as budding psychopaths, devoid of empathy and preprogrammed to commit horrific crimes. But again the reports said neither showed signs of personality disorders or traits indicating psychopathy. Similarly, there was no evidence of mental illness in either teen.

The analysis and think-pieces have started and will likely continue. There’s nothing new here. As author Blake Morrison notes in What If, his meditation on the reasons behind the murder of James Bulger in 1993 by two 10-year-old boys: “They scatter the blame at different targets – single mothers, absent fathers, schools, the Church, the Pill, the sixties, but most seem to agree that children these days are spoilt.”

Maybe our search for reason behind Ana’s murder is selfish, a vain effort to convince ourselves there is a specific thing in society we can fix so this doesn’t happen again. But perhaps terrible things like this just happen sometimes. Maybe we can better assess society not by the crime itself but by our response to it.

In this, I find some hope. Ireland has embraced the Kriégel family and taken the memory of Ana, a girl adopted from Russia who often felt like an outsider, into its heart.

Gardaí ran a flawless investigation and the rights of the two boys, the youngest in Irish history convicted of murder, were jealously guarded by investigators, lawyers and judges. (Unlike James Bulger’s killers, neither will ever be identified publicly after the trial judge ruled it would be detrimental to their rehabilitation.)

Perhaps that’s the only lesson to be drawn here, that we can remain compassionate and hopeful in the face of such evil acts, even when we can’t begin to understand them.

• Conor Gallagher is the crime correspondent of the Irish Times