A woman who accused Karen Buckley's killer Alexander Pacteau (pictured) of sexually assaulting her in 2011 warned police that she felt he'd strike again

A woman who accused Karen Buckley's killer of sexually assaulting her in 2011 warned police that she felt he'd strike again.

Alexander Pacteau was cleared of raping and sexually assaulting the woman in 2013 after meeting her not far from where he murdered nursing student Karen.

However, she was sure that the loner would go on to commit a serious crime in future, after he pleaded not guilty in court on the grounds that he was supposedly gay.

Speaking out after Pacteau pleaded guilty to murder this week, the woman told the Herald: '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.'

The shocking incident was alleged to have taken place in Baliol Lane in November 2011, less than a mile from where Pacteau met Karen Buckley.

Pacteau met the woman by chance in the early hours after a night out with friends.

Just like Miss Buckley, Pacteau initially won her trust, telling her he was looking for a taxi after leaving The Garage nightclub in Glasgow city centre.

He was then alleged to have attacked her in an alleyway after she agreed to share a cab with him.

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.

People nearby heard 'screams of panic and terror' and rushed to the scene where they discovered the young woman covered in mud. Pacteau was arrested despite initially trying to hide from officers behind a Transit van.

'He just suddenly changed,' the woman recalled.

'I said I needed to go to a cash machine for money and he just grabbed my arm and pulled me down.

'In a split second that kind stranger turned into a terrifying monster and the fear and terror I felt that night will forever haunt me.

'Pure evil': Alexander Pacteau admitted murdering Karen Buckley when he appeared at court earlier this week

'After the verdict, my world fell apart and I can't describe the agony of not being believed.'

Anxious about what Pacteau was capable of, the woman wrote a letter to the Scottish Justice Secretary.

She said: 'In my last paragraph this is what I wrote: "Please help me stop him from doing this or worse to another woman or girl."

'Reading this letter now makes me feel sick as my nightmare has come true.

'The day I saw Alexander Pacteau's name in the paper in connection to Karen Buckley I felt someone had taken all the air from my lungs.

'When I read it, my legs just gave out.

'I have relived that night over and over, at how naive and trusting I was that this stranger was genuinely trying to help me get a taxi home.'

In court, Pacteau claimed the woman slapped him when he asked about her boyfriend and the pair fell over behind a car, with him on top of her. He said he had been 'scared' and fled the scene as he was 'confused'.

Karen was described as a 'gentle soul' by her family, who said they were 'absolutely heartbroken' at her death

At one stage the twisted murderer even told jurors that he was gay – with the apparent implication that he was therefore unlikely to have sexually attacked a woman.

'I would never make an attempt to sexually assault this woman,' he said. 'I believe rape is the lowest of the low. I'd rather be charged with murder than attempted rape.'

The then-teenager denied the offence and was cleared by majority verdict at the High Court in Glasgow.

Karen Buckley, 24, was just getting to know Glasgow when she was murdered by Pacteau in April.