But all that changed when he began a torrid affair with a woman 15 years his senior, Batla's mother told The Straits Times yesterday.

'He just went crazy over her,' said Mrs Pooja Batla.

On Wednesday, her 23-year-old son was sentenced to 16 years in prison for knifing three people, including the father of his former lover, during a June 2006 rampage.

Batla was upset that divorcee Mumta Manik Shahani had broken off their relationship at the urging of her father.

Testimony in court revealed that Batla had become obsessed with the 38-year-old woman, who has a young son.

He told a psychiatrist that it was initially 'lust' that made him continue seeing the older woman and 'the sex was great'.

After their first meeting in November 2005, the couple went to a friend's house for their trysts.

Eventually Batla, who was here on a scholarship, started sneaking into her house for night-time liaisons - right under the nose of her father.

One morning, Mr Manik Ram Shahani discovered Batla in the house and slapped him. He forbade his daughter from seeing him again.

Batla, though, refused to let go and even assaulted Ms Shahani. That was the last straw and she broke up with him on June 29, 2006.

The next day, he went into her home, planning to threaten Mr Shahani into accepting him. He ended up nearly killing the 71-year-old shipping consultant and two of his maids.

The family's lawyer said Ms Shahani declined to comment.

Mrs Batla told The Straits Times that she deeply regretted allowing her son to come here.

The time in Singapore changed her son, she said. The polytechnic student began drinking alcohol and demanding thousands of dollars, which he used to court Ms Shahani.

Mrs Batla said the plan was for her son to get about $600 a month in spending money, but he kept asking for more with each passing month.

Between November 2005 and the following June, she transferred about 600,000 rupees, or nearly $19,000 at the present exchange rate, to him.

'He is my only child and I wanted him to be happy,' she said.

But Mrs Batla, who runs a fashion design firm, had to open her purse even further.

During Christmas week in 2005, her son and Ms Shahani holidayed in Goa - at Mrs Batla's expense. He also blew $300 taking Ms Shahani to a New Year's Day party.

It was a dramatic change from the scholarship winner his mother once knew.

She said: 'He was a goody-goody mama's boy, spending his free time on computer games. He was a bright student.'

khush@sph.com.sg