The main accused in the fatal gang-rape of a student on a bus in New Delhi last December has been found dead in his prison cell, an apparent suicide.
Police say Ram Singh - described as the main suspect - committed suicide in Tihar jail.
But Mr Singh's parents said there was no way their son could have committed suicide and that he had told them his life was in danger, while his lawyer said the death should be treated as murder.
Mr Singh, the driver of the bus, was one of five men being held in the case. They all deny the charges. A sixth suspect is being tried by a juvenile court.
The brutal attack on the student in December outraged India and triggered a debate about the treatment of women.
Ram Singh's lawyer, VK Anand, told the BBC he was informed about his client's death by police.
Speaking also to India's Times Now news channel, Mr Anand said it was "shocking news".
" There were no circumstances to suggest that he would commit suicide. He was happy with the trial, it was going on smoothly."
The victim's mother said she was shocked to hear of the suicide and just wanted justice for her daughter, AFP reports.
The victim died at a hospital in Singapore, 13 days after the attack.
Authorities say Tihar is one of the most secure and modern prisons in India, the BBC reports. It is equipped with CCTV cameras, mobile phone jamming devices, scanners and metal detectors.
It is also India's most high-profile prison, where a number of prominent politicians and businessmen facing trial in corruption cases have been held.
Tihar jail spokesperson Sunil Gupta told the BBC an inquiry had been ordered into the incident. He says the body will be taken for a post mortem later on Monday.