As throngs ran from the World Trade Center on September 11, the man who planned a care-free day with friends visiting from Mexico ran toward the towers.
Rafael Hernández felt his instincts kick into gear - the instincts of a first responder, of a firefighter, which he had been for many years in Mexico.
"I smelled the smoke, and the smell, the smell of a fire, sent me running toward it," says Hernández, 51, on a recent day, standing on the corner across from Ground Zero, the same corner where he stood when two planes - piloted by evil -- changed the world.
Hernández went to a firehouse across from the towers and showed his Mexican firefighter badge, which he always carries.
"Come help us," he recalls the firefighters said to him.
They gave him a jacket, a hose and into the North Tower he went - going upstairs while everyone scrambled to get downstairs.
On the 28th floor, a fire captain stopped him and told him he didn't have all the right equipment to keep climbing to higher floors.
A woman named Alison reached out to him, Hernández recalls. She was hysterical, she told him she was nine months pregnant. Her water broke, she was in labor.
"I carried her all the way down," he says. "People were pushing. She begged me not to let her go, to help her out. I promised her I wouldn't leave the building without her."
They made it outside, where he stayed with her until an ambulance took her away. Shortly after, the towers fell.
"I got away from there, but it was with great difficulty," Hernández says. "My legs ached, I was very sore, very tired. I'd just gone down 28 flights carrying a pregnant woman."
Hernández didn't return to his apartment in Queens for several months after the day of the attacks. He stayed at Ground Zero, looking for survivors, for remains. He helped with the clean-up.
He dug through debris with his bare hands at first. Toxic dust and the smell of jet fuel made their way into his body each day. Hernández and other workers - many of them undocumented people, from Latin America, who'd been picked up by contractors - eventually were given flimsy masks and gloves.
"Officials came to the site, they told us were not in danger," he says, shaking his head.
But like others who helped in the clean-up, Hernández says that he has been very ill since then, from exposure to toxic materials.WATCH:
Gone are the days when he used to run into burning buildings with heavy equipment without feeling drained because he was fit and healthy.
"Now I walk like an 80-year-old man," Hernández says. "I take a few steps, and I have to stop to catch my breath. I walk up steps from the subway to the street, and I feel exhausted."
Certain kinds of weather can leave him heavily congested. He has digestive problems and sleep apnea. His lungs have deteriorated so much that he must sleep hooked up to a respirator.
"I'd suffocate if I sleep without it," he says.
"Life is very different," says Hernández, who takes about a dozen different kinds of medication daily.
But he does not regret having helped that day.
Years later, at a Sept. 11 memorial ceremony at Ground Zero, he ran into Alison, the woman he had helped out of the tower. She told him she'd given birth to a healthy girl. She told Hernández that he was her hero, he recounts with visible pride.
"I've cried very much, because I saw so many people in and around the towers who needed help, who were wounded, who were crying out," Hernández says. "I cried because I wish I could have stayed there, rescued more people. But the truth is I wouldn't have made it out alive if I'd stayed in there a few minutes more, or gone up more stairs to a higher floor."
Many fellow immigrants from Latin America who helped out that day have fared far worse, Hernández says. Some of the immigrants, whom Hernández has met in medical treatment programs and therapy sessions, have come down with cancer. Some are depressed, some suffer from Post-Traumatic Stress Disorder, and have considered suicide.
"It was like suddenly finding yourself in a war," he says.
"I did what I did from the heart," he says. "I've been an emergency responder since I was 17. I always wanted to help people."
When Hurricane Katrina hit in 2005, Hernández went to Louisiana to help.
"No one asked, I just felt I had to lend my skills," he says. "I cannot see someone hurting and not go their aid. It's humanity."
Once a firefighter, always a firefighter, Hernández notes.
"It's a brotherhood," he says. "There's an instant bond."
Hernández, who says he has been unable to work full-time since the attacks because of his health, tries to keep positive. He has taken English classes, and now is a fluent speaker. He took a course in computing and in French.
In the future, he wants to return to Mexico to see relatives, and has discussed doing consulting in dealing with disasters and rescues.
As he has in past years, he will return to Ground Zero, this time for the 10th anniversary ceremony.
"I want to say goodbye to Ground Zero for the last time," Hernández says. "It hurts too much to be here, to be immersed in it. I'm not September 11. I want to bury it, move on. I will not come back here ever again."
Follow Elizabeth Llorente on Twitter @LlorenteLatino or contact her at Elizabeth.Llorente@FoxNewsLatino.com