Editor's note: The gang rape and murder of a 23-year-old woman in India one year ago has become a defining case in India's history. CNN's World's Untold Stories takes a look at the events surrounding the incident through the eyes of those most closely involved -- the girl's parents, the chief police investigator, and one of her doctors.
(CNN) -- The colorful, busy streets of New Delhi, India's capital, are a mixture of old and new. Some people have modern attitudes, while others remain rooted in ancient values.
A 23-year-old female medical student from Ballia, in India's Uttar Pradesh State, had set out to change that. She had plans to give free medical care to the needy, to provide for her family, and to change those perceptions that a woman can't dream big in a traditionally male-dominated society.
She was the bridge between India, old and new.
But what happened to her on December 16, 2012 would be the country's tipping point -- a rape that shook the nation.
In India, there are laws for the protection of rape victims. These laws prohibit naming or showing a victim, which is why we will refer to her only as "Nirbhaya," one of the many names given to her by the public and the Indian media.
In Hindi, it means "the fearless one."
A family's 'pillar of strength'
In an apartment provided by the government, the young woman's mother, Asha Devi, said her daughter had dreams of providing free medical care to those who could not afford it. She also said her daughter was a "pillar of strength to the family," which includes two brothers.
Nirbhaya's father, Badrinath Singh, a baggage handler at the Delhi airport, earned barely enough to make ends meet. He also shared his daughter's dream.
"We did everything we could for her education," he told us. "I worked double shifts, sold our only piece of land in the village and went beyond my capacity so that she could study. Doing a 16-hour shift at my age is very difficult, but I still did it."
Last December, Nirbhaya was scheduled to start an internship. Her parents wanted her to have some fun. She thought of going to a movie. Her mother agreed -- otherwise, she would not have had a chance to relax for another few months.
So Nirbhaya and a male friend set out to an upscale Delhi mall to watch Ang Lee's "Life of Pi."
That night was December 16, 2012. The next time Singh and Devi would see their daughter, she'd be fighting for her life.
A bus ride from hell
When Nirbhaya and her friend finished the movie, they tried to find an auto rickshaw, a three-wheeled taxi, to take them back to the outskirts of the city. It was a 45-minute drive no one was willing to take that night. Instead, they boarded a white bus at a busy bus stop.
It was not late at night. She was not out alone. They were taking public transportation. She had done all the things women all over the world are told to do in the interest of safety.
It was not enough.
On the bus were five other male passengers and a male driver. At first, nothing seemed out of the ordinary. But shortly after they boarded the bus, her male friend was beaten, and the young woman was dragged to the back of the bus and violently gang raped. The men took turns, even violating her with an iron rod. They beat them both within an inch of their lives, as the bus drove around Delhi for over an hour.
Then, the men dumped them on the side of the road, left for dead.
No one would help them, until a few police cars showed up. According to the male friend, the policemen weren't sure who had jurisdiction. They waited for an ambulance that never came, he said. So he carried his bleeding friend to a police van, and they took her to Safdarjung Hospital.
"The atrocious, unbelievable injuries that she had sustained, we had never seen before," said Dr. MC Mishra, one of the many doctors who would treat her in the coming days. "In my almost 40 years of career, I have never witnessed such a horrific brutality by human beings."
'I will get better soon'
Her mother waiting at home sensed something was awry.
"That day she didn't call back after leaving home," she said. "Usually she would call us and inform as soon as she'd reach the place. It was half past eight and we hadn't heard from her. We tried calling her but she didn't answer the phone."
They waited and called again.
"It seemed as if she dropped her phone while trying to answer and the line got disconnected," her mother said.
They called again, but this time her daughter's cell phone was switched off.
When the phone finally rang, it was not their daughter on the other end. It was someone at Safdarjung Hospital, telling them their daughter was in surgery.
When they found their daughter there, they were speechless.
"What was in front of our eyes what hard to even imagine," Devi, her mother said. "We didn't know how to react for the first few moments."
Their daughter lay on a stretcher, but she was conscious.
"She looked at me and started crying," her dad recalled.
He tried to soothe his only daughter. Keep calm, and do not worry anymore, he told her. He would take care of everything, he assured her.
"I couldn't be with her for long," he said. "I just couldn't see her in so much pain. I would keep visiting her every few hours but wouldn't stay longer. I'd go and pat on her head. At times she'd be sleeping. She would smile whenever she saw me. But I didn't have the courage to see her like that."
Nirbhaya told her mother they beat her badly.
"What could she say... even I didn't have the courage to ask her anything," Devi said. "She was in great pain, so we never asked her anything."
Even in so much pain, Nirbhaya tried to reassure her parents.
She kept telling them: "Don't worry, I'm doing better and will get better very soon."
Rape that shocked the world
Unfortunately, what happened to Nirbhaya is not uncommon in India. The country, with a combination of conservative, male-dominated thinking and weak law enforcement, has recently been in the spotlight for widespread violence against women. But it is not a new problem.
In 2012, there were 706 reported rapes in Delhi alone. Nationwide, a woman is raped every 20 minutes. But those numbers don't tell the whole story. Most rapes are never reported -- and never prosecuted -- mainly to avoid the stigma of damaged honor in a country where victims of sexual assault are often viewed with suspicion.
But it was what happened next that made this case different.
Within days, word had spread across India and around the world. The brutal nature of the attack had struck a nerve. And in their thousands, Indian citizens -- both men and women -- took to the streets in protest. Enough was enough, they shouted. It is time to protect women in India.
In the hospital, Nirbhaya and her parents weren't aware of what was happening until a doctor showed them a newscast. They saw the protesters. They also saw the police trying to keep them at bay with water cannons.
"That day I felt whatever was happening wasn't right," said Nirbhaya's father. "Our daughter's life was already at stake. If these protests took anymore lives, it would have been worse. It was winter and water cannons would have caused much harm. At that time, through media, I appealed to the public to maintain calm.
"We never thought something like this could ever happen to us," said her mother. "It shook the entire nation and led to public outrage on the streets. After seeing all that, we felt humanity still prevails on this earth."
A fight to the end
Meanwhile, lead police investigator Chhaya Sharma and her team worked tirelessly to find the rapists. In the hospital, Sharma said, Nirbhaya was crucial in providing clues to the police.
She and the male friend helped lead investigators to the white bus, and to its driver -- Ram Singh -- who had driven the bus around as the gang rape took place. He eventually led them to the other five men who had been on board that night. By December 22, according to Sharma, all six suspects had been arrested.
But back in the hospital, Nirbhaya was slowly losing her fight. The vicious attack had damaged her intestines, which had to be removed. The decision was made to transfer her to a hospital in Singapore. But she developed an infection, and later died there on December 29, 2012.
"Her brothers, father and I had gone with her to Singapore," said Nirbhaya's mother. "All four of us were standing right next to her when she took her last breath. What could we do? We quietly kept on gazing at her from one corner, crying. Being in a foreign land we didn't know anybody, we couldn't even understand their language so we had no idea what the doctors were saying among themselves."
Then doctors came to them. "Sorry, there's nothing we can do now."
"That's when we realized our daughter was no more," her mother said.
With heavy hearts, Nirbhaya's family returned to India at the end of 2012 with their daughter's body. When the news spread that she had died, anger turned to grief, and protests became vigils.
"To tell you the truth, I saw on TV what was happening outside, but could not register anything, as our minds were preoccupied by something else," said Nirbhaya's father.
"We understood the magnitude of the impact of this incident only once I reached my native village with my daughter's ashes. That's when I figured it wasn't ordinary. People kept coming and sharing with us all that had happened in past few days. So after listening to all those stories, I realized we are not alone, we have full support of our fellow citizens, media and police in our fight for justice."
That fight for justice would be a long and complicated road. The charges against the accused were rape, kidnapping and murder. With the public in the streets once again, the prosecution decided it would fast-track the trial.
In the courtroom, Nirbhaya's parents came face-to-face with her alleged attackers. They were forced to hear accounts of the unspeakable violence against their daughter, time and time again.
"The convicts showed no remorse," said Nirbhaya's mother. "They were not even ashamed of what they had done. They were very casual, sometimes even cracking jokes during the trial."
"It didn't really affect me looking at them," said her father. "If there are demons in society then there are also angels. Because of their deeds, our family is suffering, and so must be theirs. Whatever happened has caused pain on both sides. We are suffering as we lost a loved one. Their families will suffer if they lose them. People like them don't just ruin one family but thousands of families because of their evil acts."
The trial went on for months. Then, in March 2013, the bus driver Ram Singh was found dead in his jail cell, where he had apparently hanged himself. And the sixth suspect, a minor at the time of the attack, was convicted in a juvenile court. He was sentenced to only three years in a rehabilitation center, prompting further outrage from the public and the family.
The fate of the remaining four suspects remained with the fast-tracked court.
The guilty verdict the entire country had been waiting for came in September.
In a stunning move for a country that rarely condones the death penalty, the four convicted men were indeed sentenced to die.
Ten months since the death of their daughter, Nirbhaya's parents finally felt they had justice.
"The incident sparked reactions from across the nation," said her mother. "There was so much public outrage due to the brutality involved. The convicts were also handed out punishment according to the crime they committed. So I am hopeful it should set a precedent and help change the way people think."
A brave heart
To India, Nirbhaya has become a symbol of bravery, courage and change.
But to her parents, she will always be their baby girl.
"Our grief can't be measured," her father said quietly. "Whatever maximum limit you can think of will still fall short of the pain we went through. I don't have words to describe my loss. We had lost sense of everything -- from eating to sleeping to everything else. We had lost track of day and night. Everything had come to a standstill."
Since the attack, police say more women are reporting crimes against them.
India's laws have also been changed to widely expand protection of sexual assault victims.
That will be the lasting legacy of Nirbhaya, a girl India has never met in person, never seen.
The girl who did not allow anyone who came in contact with her to feel sorry for her situation. The girl who reassured her parents she would be OK. The girl who helped police track down her attackers. The girl who lived for nearly two weeks, when no one gave her a chance to make it through the first night. The girl they call Nirbhaya, "the fearless one."
"My daughter put up a tough fight against her attackers and didn't give in until her last breath," said Nirbhaya's mother. "I want her to be remembered as a brave heart."