He is a brilliant student with a dark secret. The police on Monday revealed what has been going on in the dangerous and perverted mind of the IIT student arrested for murdering a Naga girl.

Chilling details are emerging now on how the 19-year-old, Ramchanphy Hongray, was so brutally killed, a tragedy that could further alienate students from the Northeast.

'A maniac and a pervert', words used by the Delhi Police to describe IIT student Pushpam Sinha, now a killer.

Just a month ago, the girl had come to visit her sister who works in Delhi. It was on Diwali that she got to know Pushpam, who lived next door.

According to the police, the IIT student was mentally disturbed. He had presumptions about the girl but when she spurned his advances, he feared that she might complain to the police against him. He panicked and murdered her.

The manner of the crime revealed a cold, calculating killer.

"Accused put her face on the gas burner and burnt her face and torso. He had the entire sequence of events in his head and gave alibis so that no one suspected him," said Dhaliwal, DCP, South Delhi.

Pushpam, the son of an aeronautical engineer and a graduate from the Indian Institute of science, had a brilliant academic record, but he was always a recluse. The police say his room had telltale signs of a perverted mind.

There was lewd graffiti all over his wall, and his dairy revealed he was frustrated at not being married. He also mentioned he was blacklisted for bad behavior in college. His laptop had pornographic content, and he allegedly bought gifts for girlfriends he never had.

His father in Bihar, an aeronautical engineer, is in shock.

"My wife is very unwell. I have nothing more to say," said his father.

And in Manipur, another family also struggled to come to terms with their loss.