Alexander Pacteau family friend reveals details of Karen Buckley's depraved killer's childhood

The 47-year-old, who worked with the brute's father Guillaume, said: "I remember him as a little boy, but he turned into a monster."

It comes after the Evening Times revealed how a young woman who accused Pacteau of a sex attack warned authorities about him.

Speaking about her ordeal for the first time, she told how she wrote to Justice Minister Kenny MacAskill telling him she believed Pacteau would strike again one day.

Since our exclusive interview with Pacteau's accuser, calls have been made for the case to be re-investigated under double jeopardy laws.

Last week, 21-year-old Pacteau admitted murdering Irish nurse Karen Buckley by repeatedly beating her with a spanner, strangling her and dumping her body in a barrel of caustic soda.

The family friend, who wishes to remain anonymous, worked with Guillaume, 45, as he set up his courier firm at the family home in Bearsden.

They told the Evening Times: "Alex was only four or five-years-old when I knew him, but you could tell he was a troubled child.

"I've never met a more obnoxious child.

"His bad behaviour was non-stop and he was constantly attention seeking.

"Between the tantrums and throwing his dinner about, his parents were always shouting at him.

"I've never seen a little boy like him and it wasn't something he grew into - he was born that way.

"Just a really bad wee boy, he was often refereed to as 'trouble'.

"You could always tell something wasn't right and I often wondered what he would turn out like when he grew up.

"But I could never have imagined this. I was absolutely sick when I found out what he had done."

Pacteau's French father, Guillaume, ran his businesses while his mother Noreen raised Alexander, his sister and two brothers.

The family was "very well-off", according to close friends.

Our source added: "If ever there was a family that you thought would go onto great things, it would be them.

"I can't begin to imagine how their wee boy could grow into someone capable of such a horrible thing."

Pacteau attended Baljaffray primary school and later went to Kelvinside Academy, a private school in the West End.

When he was 17-years-old, he was accused of attacking a young woman in a Glasgow lane in 2011.

He denied the charges of attempted rape and sexual assault and was cleared by a majority verdict at court in Paisley in 2013.

Dr Mairead Tagg, a leading psychologist, said: "I personally think this case should be reopened."

His accuser, who is now 28, met Pacteau by chance after a night out with friends in Glasgow.

He preyed on her trusting nature and struck up a conversation while they both waited for a taxi.

She said: "From the moment I knew he was found not guilty in my case, I knew in my heart I would see his name again one day because he had hurt someone else.

"I had a horrible feeling I wouldn't be the last person that he hurt. And every day since that day this thought has tortured me."

Pacteau was alleged to have attacked her in a lane after she agreed to walk with him to try to get a taxi.

He was accused of forcing her to the ground, putting his hand over her mouth, carrying out a sex act and attempting to make her carry a sex act out on him.

Her ordeal only ended when people, including two men on a nearby balcony, heard her screams and rushed to her aid. Pacteau was arrested a short time later.

Meanwhile, detectives are appealing for any other potential victims of Pacteau to come forward.

Detective Superintendent Jim Kerr, from Police Scotland's Major Investigation Team, said: "Our investigation and subsequent report to the Crown Office and Procurator Fiscal Service, documented what police currently know about the activities of Alexander Pacteau."

He added that if anyone had any information about other incidents that Pacteau may have been involved in then "we would ask that they contact police".