IT was a murder that repulsed Scotland. The remains of a beautiful young Irish woman, found with horrific injuries, dumped in a barrel of acid at a farm on the outskirts of Glasgow.

The victim was 24-year-old Karen Buckley, from Cork, who had come to study occupational therapy at a city university. She spent six happy weeks in Glasgow before her life was brutally snatched away.

A chance meeting with her murderer Alexander Pacteau, who had been previously accused of sexual assault and attempted rape around a mile from where he met the qualified nurse, led to her "senseless" violent death.

The killing gives a chilling insight into the mind of the murderer - and it reveals a budding serial killer, a psychopath driven by inadequacy and hated of women who would have went on to kill again had he not been caught. Experts believe it is unlikely there are not more victims - perhaps of violent assaults or sexual attacks - out there.

Dr Mairead Tagg, a psychologist and expert witness on the abuse of women, said: "The lassie was just so unlucky, it was nothing she said or did. She was marked for destruction as soon as he saw her."

The 21-year-old killer exploited his victim's trusting nature and offered her a lift home from the Sanctuary nightclub in the west end of Glasgow. Within 18 minutes, she was dead.

Experts believe he had ventured out that night deliberately looking for a victim.

Outwardly Pacteau, a quiet privately educated self-employed salesman who enjoyed drag racing and spending time with his friends, was "normal".

But the brutal murder of Karen Buckley and attempts to dispose of her body in an acid bath, point to a deeply enraged, calculating and destructive young man.

Pacteau was inwardly consumed by a life-long rejection by women, according to close friends, and he had come to hate women.

"He is definitely a sociopath and quite possibly a psychopath, he shows no guilt or remorse", Tagg added.

"With this attack, he was re-enacting rage against women in general, or one woman in particular.

"It was a personal attack, but not a personal attack on Karen Buckley. It was personal for him. The murder itself shows how he tried to obliterate her face.

"He carries a lot of rage and hostility and there's no doubt he was looking for a victim that night.

"He has grown up without a moral compass and shows no remorse, which makes him an extremely dangerous individual."

The apparent trigger for the murder - a trivial argument with the 24-year-old nurse over a comment she made - was the catalyst for a pre-planned violent fantasy.

And although his victim was killed during an act of rage, experts believe Pacteau carefully planned the aftermath of the killing for months, even years, beforehand in readiness for the day his fantasy turned into reality.

Despite Pacteau's claims that a "trivial argument" in his car led to the murder, Dr Ian Stephen, an expert in forensic psychology, explains what makes men like this commit the most horrific crimes.

Stephen, whose work was the inspiration for the TV series Cracker, believes rejection may have been the trigger for the attack.

The former director of psychology at Carstairs State Hospital, who also worked with the Scottish Prison Service as a specialist in violent offending, said: "People like him react to triggers.

"The likelihood is that he has been inappropriate, she has rejected him, and that is when he has gone into "killer mode".

"And once the trigger has happened, it has happened and there is no going back. He is a highly dangerous individual.

"If he had been successful in getting away with it, and still on the street, another one would have followed."

Pacteau's behaviour around women indicates he was seemingly unable to sustain emotional relationships with the opposite sex.

According to his friends, he frequently paid prostitutes for sex - another sign of an emotionally dysfunctional man, whose fear of rejection stopped him from forging real relationships.

One close friend, who did not wish to be named, said: "He never had a girlfriend and he knew he wasn't an attractive guy.

"I think that's why he was so awkward around girls, especially pretty ones. He knew he had no chance with them and that's why he never tried.

"When he spoke about going to prostitutes, he would say he liked that he could control them and that's why prostitutes were better than having a girlfriend."

Stephen described Pacteau as a "sophisticated Jekyll and Hyde character".

He said: "He (Pacteau) had created a fantasy world. The death itself was impulsive, but what happened after was a cold reaction.

"He was in neutral mode. I think he would have seen her body as a corpse, not as a person. After he goes into "tidying up mode", he would have become clinical, simply making plans.

"He is cold and detached. He will see that she deserved it. But he would have got some enjoyment out of what he did."

Pacteau, who has a younger sister and two brothers, grew up in the wealthy Glasgow suburb of Bearsden, but his parents split when he was a teenager.

He remained close to his mother, Noreen Pacteau, and had dinner with her, her partner, his grandmother and his brother shortly before he killed Karen Buckley.

Asked how Pacteau's fantasy of violence could have grown, Stephen added: "His relationship with his mother, the relationship between his mother and father, how people around him treated each other, and watching TV and playing games. There are a combination of factors which can lead to this."

Pamela McElhinney of Glasgow East Women's Aid and an expert in male violence towards women, believes Pacteau's "formative years" may have unlocked his fantasies and allowed him to live out a monstrous persona.

She said: "Alexander Pacteau made that ultimate choice to take Karen’s life, and there is no justification on earth for his decision.

"The individual pathology of perpetrators is obviously paramount and therefore his formative years are relevant, and factors such as early attachment with parents and particularly the mother is a contributory factor.

"Cultural and social influences should not be minimised in a violence against women context."

However, there were warning signs about Pacteau's attitudes and behaviour towards women when he was accused of sexually assaulting a young woman in a Glasgow lane in 2011.

The alleged incident bears striking similarities to the attack on occupational therapy student Karen Buckley.

The woman, who was 24-years-old at the time, met Pacteau by chance after a night out with friends in the city's Woodlands Road.

Just like Karen Buckley, Pacteau preyed on her trusting nature and struck up a conversation while they both waited for a taxi.

He denied the offence and was cleared by majority verdict at court in Paisley in 2013.

When Pacteau parked his Ford Focus in Kelvin Way at around 1.10am on Sunday April 12, Karen Buckley's fate was sealed.

Pacteau attacked her, repeatedly bludgeoning her with a spanner.

She struggled, but he throttled her as he tried to muffle her terrified screams.

As Pacteau begins his life sentence, one critical question remains: how did tragic Karen Buckley fall into his hands?

Did she ask him for directions or did she let her guard down and accept a lift from him?

Like many psychopaths, Pacteau has withheld this information and why he attacked her as part of a "game of power and control", psychologists believe.

Tagg said: "In his mind, there will be a reason why he carried out this horrific attack. And this is typical behaviour of a psychopath, they make you work for every little bit of information, but often it isn't the full truth."

Tagg added that refusing to disclose details is among the few things he still has control over.

She added: "It's very much about power and control for him.

"Pacteau is a serial killer in the making, there's no doubt about it. The best prediction of future behaviour is past behaviour.

"He must be carefully monitored for the foreseeable future. From the first allegation in 2011, he has dramatically escalated and I find it very strange that he hasn't committed any offences between the ages of 17 and 21.

"I would be very surprised if there aren't more victims out there."