Wafa al-Biri, a 21-year-old Palestinian woman with a lovely face and a quiet voice, seems an unlikely candidate for a suicide mission.

Yet her greatest wish, she told reporters, was to kill 30 to 50 Jews, including children.

The motives of suicide bombers are many, mysterious and murky. And rarely are they as stated by the bombers on camera.

Wafa's case sheds some light on what is to many an incomprehensible phenomenon. Why do people become suicide bombers? More specifically, if male martyrs reputedly get 72 virgins in paradise, what do women suicide bombers get?

Starting with a thank-you note

Wafa, who is from a Gaza slum camp, claimed she always wanted to be a martyr. She says the Israelis kill and maim her people and she wants to do the same to them.

Only two months earlier, Wafa's family wrote a thank-you note on her behalf to Soroka hospital in the southern Israeli town of Beersheba.

They thanked doctors and nurses, especially Igor Resnik and nurse Mazal, for their "great efforts and wonderful, warm attitude" in helping Wafa survive burns over 45 percent of her body. A gas cooker had blown up while she was making dinner, burning her everywhere except her face.

Dr. Yuval Krieger, the Israeli doctor who treated Wafa, said she arrived from the Arab hospital of Shifa with infected burn wounds. The treatment she had received before ariving at the Israeli hospital was not good and her burns were dressed incorrectly.

"Did you save her life?" Krieger was asked.

"I believe so, yes," he replied.

But Wafa didn't arrive for Monday's 8 a.m. appointment. "I didn't think much about it. I just marked her as one of the people who didn't show up," Krieger said.

Wafa had begun the journey to her appointment with Krieger, arriving at the Erez border crossing from Gaza into Israel around 5:30 a.m., armed with a letter detailing her appointment and her official permission to cross into Israel for humanitarian reasons.

But that wasn't all the young woman was armed with. She carried a 20-pound bomb inside her underwear. Her target was the outpatient clinic of Soroka hospital and, inevitably, the doctor who saved her life.

Descent

But how did the grateful young burn victim become a suicide bomber?

One thing is for sure: It wasn't the religious and nationalist reasons she stated to reporters after soldiers stopped her at the border crossing, made her undress and discard the bomb, which a robot then detonated harmlessly.

It also wasn't her burning desire since childhood to be a martyr, as she claimed. It also wasn't because of the Israeli occupation, which was the motivation of her handlers from the al-Aqsa Martyrs' Brigades, the militant group that she said gave her the bomb, drove her to the crossing and gave her instructions.

We know these things because of another young woman, Latifah, whose son shared a ward with Wafa in the Soroka burns unit. Latifah met Wafa in the hospital and they became friends. At her son's bedside, her hands folded, Latifah recounted to NBC News what Wafa told her in the month they spent together, chatting daily.

"Before she was burned her mom told me that Wafa was a very funny girl, very active, laughing a lot," Latifah said. "But after the burning she became very tired and depressed. And often Wafa said to me, ‘I can't live like this, I am so ugly, I want to commit suicide.’ She had a fiance. But after the accident he left her. Then she kept crying, ‘Nobody will want me, I am too ugly, my body is scarred everywhere’."

When Wafa was released from Soroka, she didn't want to leave, Latifah said. "She was screaming, shouting, ‘Please don't let me go. I am better here. I'm going to die.’ But they made her leave, on a stretcher, and they took her home to Gaza."

Later Latifah visited her new friend in the small home the family occupies in the Jabalya slum. They're nice people, poor people, simple people, Latifah said.

But with her ugly wounds, Wafa lost her friends. She was lonely.

Then, Latifah continued, "Suddenly she said, ‘I want to commit suicide. If there is anyone who will give me a bomb to blow myself up I will do it.’ Her mom shouted, ‘Shut up — don't say that. We don't need more problems’."

Wafa's mother told Latifah that her daughter was sick, unhappy, and might need a psychiatrist. "But her brothers said, ‘No, people will talk about us, they'll think she's crazy. We should take her for a walk. Maybe she will change her mind’."

Worst of cases

Krieger pointed out to us that patients with severe burns usually become depressed and proper psychological counseling is critical, even in the best of cases.

In the Jabalya slum, jilted by her fiance, surrounded by shamed brothers, scared parents and poverty, Wafa al-Biri was the worst of cases.

She was easy pickings for someone with a bomb and a cause. According to Wafa, the al-Aqsa militants came knocking. Here was a vulnerable young woman, willing to die, and moreover with the golden ticket — a pass for humanitarian reasons to a hospital in Israel.

After all, who would check the underwear of a sick young woman on her way to the hospital?

A hundred patients mill around the outpatient ward in the morning. Wafa could die a hero and a martyr with Jewish blood on her hands and not just her veins, after the dozen blood transfusions she received in the Israeli hospital.

And she would have, if the Israeli secret services hadn't received a tip that a female suicide bomber was on the way and alerted all Gaza border crossings. When Wafa showed up Monday morning, the soldiers were ready.

Time freezes

Wafa found herself alone that dawn, locked between a metal turnstile behind her and a metal gate in front, a soldier shouting instructions through a loudspeaker to drop her pants and the bomb, and two cameras recording her every move. She was caught.

Frustrated, Wafa decided to die anyway. As she flinched to her left, with her deformed right hand she brusquely pulled the detonator string in her right pocket. Time froze in that instant. But instead of exploding in a blast of smoke, flame and burning air and lethal metal, the string came out in her hand. Wafa lived.

Thrusting her hand into her pocket and fiddling with the detonator, Wafa tried again and again. Then, in a primeval scream of rage and frustration and smacking her neck again and again, Wafa burst into tears, condemned to live.

As for Krieger, he's alive too and so are all the nurses and patients that would have died if Wafa had succeeded in her attempt at mass murder.

"That evening I came back home and one of my friends called me and asked if I'm going to the synagogue to pray. I said why?" he said.

"Don't you know? Your life has probably been saved by the soldiers. You should send them flowers and say thanks to God. And that's what I'm going to do."

Asked if he would think twice the next time a patient arrives from Gaza, he said no, the hospital treats Arabs from Gaza every day.

But then Krieger paused and the pause stretched. "Let's say that we treat everyone with no questions, and we always will, wherever they are from," he said finally. "But I never imagined that a patient would try to hurt me. We will have to look more carefully at our security."

For the medical staff of Soroka hospital, a sick person is a patient. But for the Arab militants of al-Aqsa Martyrs' Brigades, someone sick like Wafa is just a vulnerable person waiting to be manipulated, a potential suicide bomber.