Each fragment of life recovered from the 10-story mountain of World Trade Center rubble - hands, feet, torsos, skulls, slivers of bone small enough to slide into tiny test tubes - was examined and sorted by Amy Mundorff, the city's forensic anthropologist who narrowly escaped death that morning herself.
She knew she couldn't put the lives back together, but for three years her work has helped the medical examiner identify thousands of remains, bringing relief to families and helping her work out her own survivor's guilt.
"I survived - this was the least I could do," said Mundorff, who was part of a medical examiner's office team that arrived at the trade center as the 110-story skyscrapers were still burning.
When the first tower collapsed, she was thrown 40 feet, broke two ribs, hit her head and suffered two black eyes. But she went to work two days later to begin sorting through the remains of nearly 2,800 victims. Three years later, with about 1,570 people identified, the medical examiner's office is still working on the task - considered the largest DNA identification project ever.
For months, refrigerated trucks carried thousands of remains from the site to the medical examiner, larger parts in body bags and small pieces in red plastic biohazard bags. Wearing gloves, a mask and a plastic gown over medical scrubs, Mundorff stood over a gurney in a stifling hot tent and opened each bag.
First she threw out chicken bones and other waste from the trade center's restaurants that might have been mistaken as human remains. Then she sorted the human parts, looking for anything unique, like a healed fracture, that might help identify the victim. Parts that were not clearly from the same person were placed in separate containers, so the medical examiner could DNA test each piece.
Early on, there were whole bodies - 291 people were recovered intact. One evening as she headed home after an exhausting day, Mundorff recognized on a wall of posters of missing trade center victims a photo of a person whose body had just been found.
She wasn't ready for that. It was too real.
"In the beginning, I couldn't know these people. It was too overwhelming," said Mundorff, who is 35 and married. Later, she would look them up to learn more about their lives.
Smaller pieces that didn't conjure up the image of a living person were easier to deal with.
But many bags of remains also contained personal belongings like wedding rings, clothing and even photographs. Once she opened a bag to find a man's remains along with a particularly heartbreaking photo of his child.
For months, what she found in those bags left her in tears. Sometimes, she wept by the side of a gurney, where she worked with a team of law enforcement officers, usually FBI agents and New York City police officers.
"Behind your mask, you can cry pretty good without anyone noticing," she said.
They worked 12-hour days, six or even seven days a week. Blood and matter spattered their shoes, and the tent either reeked of decomposing flesh or the tangy sweet odor of burnt trade center debris.
"Sometimes you just wanted to close your eyes. A lot of people overcame fears," said Woody Millwood, a NYPD detective, now retired, who worked at Mundorff's side for several months. "You have to have an understanding that you're going to come through this all right, that God doesn't give you anything that you can't handle."
The tiny 5-foot-1 Mundorff stood tall among those burly detectives, unafraid to call out orders and tell people to get out of her way as she worked furiously through the mess. But she could hardly finish her sentences by the time she staggered home, emotionally drained and nearly catatonic. Her husband, whom she married barely a year before Sept. 11, always had dinner waiting.
People who know Mundorff describe her as strong, but she says her husband, Kurt, was her lifesaver at her lowest moments - when a siren, a loud rumbling noise or a burning smell brought it all back. "I'd always tell my husband, 'I'm never going to be the same again,'" she said.
For nine months, rescue workers combed for human remains in the more than 1.5 million tons of rubble. Twenty-thousand pieces were recovered, more than 6,000 small enough to fit in a five-inch test tube. The most matched to one person exceeded 200.
After workers stopped recovering parts, Mundorff handled requests from the DNA lab when it needed a sample snipped from remains. She also double-checked remains before they were released to families, to ensure that nobody received the wrong piece.
Last month, Mundorff decided to leave the job and finish her dissertation. It's not exactly an escape: the topic is the recovery of fragmented remains after mass disasters.
She hopes the change, which also means a move across the country, will allow her to begin healing.
But she also agonizes about leaving before the medical examiner declares an end to the identification project, which could come this fall. Officials don't expect to identify every victim, because some were essentially vaporized. Other remains were so damaged by fire and other elements that they have not yielded usable DNA - those will be preserved and retested as technology improves.
"She'll be missed. She became the gatekeeper of remains," said Robert Shaler, the forensic biologist who oversees the project and hired Mundorff in 1999. He described her as meticulous, noting one occasion in 2002 when Mundorff caught a mistake that would have sent a torso to the wrong family.
Even though she handled thousands of body parts, Mundorff says she remembers many, and could describe them. Like the time that an unusually long leg caught her attention.
"This person must have been so tall," she remembers thinking. Weeks later, after the leg was identified and she learned who the person was, she looked him up and read that he was, in fact, quite tall.
It took some time before she was able to read about the victims, but eventually she sought out their stories - hundreds of strangers she already knew intimately.