Responding to widespread shock and public criticism, India’s government on Monday ordered an investigation into the prison death of one of the men charged with the gang rape of a young student in a moving bus last year, a horrific incident that sparked a national uproar over women’s safety.

A prison guard found Ram Singh, the bus driver and alleged leader of the gang that raped and fatally wounded the young woman, hanging from the ceiling of his cell at dawn Monday.

Although many anti-rape protesters had demanded that the accused men be sentenced to death, and Indians were expecting the harshest verdict from the court, Singh’s suicide came as a jolt to the public.

Singh’s lawyer charged foul play, Singh’s father said it was murder, and Home Minister Sushilkumar Shinde called it “a major security lapse.” Anti-rape protesters questioned the security inside India’s fortress-like Tihar Jail, the nation’s largest such facility.

Hours after the news of the prison death, another defendant in the case pleaded, with folded hands, with the judge in a city court: “Shoot me, but don’t send me back to jail,” according to his lawyer, A.P. Singh.

What flummoxed Indians was how one of the country’s most closely watched prisoners might have managed to hoodwink not only guards but also his cellmates sleeping nearby.

“Gymnastic dexterity, phantom-like stealth? An unbelievable suicide. Can the mysterious death of Delhi gang-rape prime accused be taken at face value?” asked the Times Now news channel in a prime-time debate.

Prison officials told reporters in New Delhi that the 33-year old Ram Singh had chatted with his three cellmates late into the night. But after they fell asleep, he hanged himself from a grill on the ceiling by tying his clothes and pieces of blanket together to make a rope, authorities said.

Singh and the other accused men had earlier been kept under a strict suicide watch in the prison. But there was no surveillance camera inside Singh’s cell, and a night patrol guard had last seen him at 2.30 a.m. during his round, a prison official told reporters.

“This suspicious custodial death or killing raises serious questions about the state of our legal system and the terrible state of our jails,” said Kavita Krishnan, one of the leaders of the anti-rape demonstrations. “Are we saying we know how to conduct the judicial process in a democracy, or are we sending a message that we can satisfy ourselves with the extrajudicial death or killing?”

Krishnan said there are a lot of questions about the circumstances in which Singh died. “I am not confident we will ever get to the truth,” she added. “The prevailing public mood is such that everybody presumed that this man was guilty, and they are now saying, ‘Good riddance.’ ”

Mangelal Singh, Ram Singh’s father, told reporters that it was not a suicide but a murder and that his son had been raped in prison by other inmates.

V.K. Anand, the lawyer who was defending Singh, said: “There is some foul play; he cannot commit suicide. He is not such a person that he can commit suicide. He was very happy with the way the trial was going on.”

The gang-rape victim’s brother told the news channel CNN-IBN that he does not blame the prison authorities. “He must have felt guilty, he had done such a wrong thing,” the brother said on TV. “But he should have been hanged in public.”

The young woman, who was critically injured during the assault, died in a Singapore hospital on Dec. 29.

Earlier in December, there were reports in the Indian media that one of the five suspects in Tihar Jail had been beaten up by other prisoners.

In an interview with The Washington Post in January, an officer said that one suspect accused in the gang rape, a minor, had to be held separately because other inmates of the juvenile home were threatening to beat him.

A post-mortem of Singh’s body will be conducted Tuesday at a government-run hospital in the Indian capital.