I remember vividly the terrible day when our lives (our world) changed forever. I was listening to the radio in my apartment, a few blocks away from Ground Zero, when the plane hit the first Twin Tower and I heard the cries from the street below: "Oh, no, no, no!" "Oh, my God!" I ran downstairs just in time to see the second tower crumble like a sand castle. It was 9:59 am.

I joined others rushing to the spot when a large group of people came running back shouting: "Go back, go back, for God's sake, go back!" We rushed back only to discover later that it was a false alarm and that there would be no more attacks on the towers after the second plane hit. Without fully understanding the significance of events, I felt - like so many others - that a relatively peaceful way of life had been replaced by a darker, more sinister one. A great sadness came over me.

Soon after, we learned the details of what had happened, and heard stories and saw pictures of those who had thrown themselves voluntarily to their certain deaths rather than remain trapped inside an inferno. Richard Drew, who photographed one of the iconic images of that fateful day, the "Falling Man," where you see the lonely image of a man falling to his death with one of the towers in the background, said recently that for him that was the image of the Unknown Soldier. An estimated seven percent of those killed in the attack of September 11 did so by jumping into the void from their offices.

We also learned of the heroic conduct of hundreds of firefighters who risked and lost their lives. One of the firefighters was a 34 years-old Argentine man named Sergio Villanueva. That day, about an hour before the attack on the Twin Towers, he had finished his shift. But, like so many other days, he had stayed to have breakfast with his peers. When they heard news of the attack, he decided to join his fellow squad members and went with them to the towers to help in rescue efforts. Neither he nor his fellow brigade members ever returned.

We also heard heartbreaking stories about people we knew who were killed in the towers. One, the son of friends, had just enough time to call his brother and tell him, "Please tell Mom and Dad that I love them a lot as I love you," before the line went dead. To this day his parents have not regained their joie de vivre. Or the employee of a large company who left the towers, called his wife to say he was fine after the first tower had been hit, then returned to retrieve documents from his office and died shortly afterwards when the atrocious fire ravaged his office.

What promised to be a peaceful September morning turned into a nightmare. As usual, that day (a beautiful sunny day with a very clear sky) we woke up with my wife around 7 am and, after having breakfast, she had left for her work on Long Island, a distance of about 45 minutes from home. I was planning to have a working lunch at the United Nations headquarters.

After the second attack on the towers I hastily tried to contact my wife at work. It was impossible to communicate by phone with my wife on Long Island. However, I learned that it was possible to communicate by telephone with Queens, where a medical colleague, Dr. Juan Rivolta, lived. I called him immediately to see if I could communicate with my wife through him. I quickly summarized what had happened. He initially thought that I was joking but changed his mind when he heard the desperation in my voice and finally was convinced when I told him to turn the TV on and see what was happening.

Juan was able to communicate with my wife and told me that she was safe. When we spoke later that day she explained that soon after arriving at her college someone had called the office and they quickly turned the television on and were able share the horror of what was happening. Since virtually all roads leading to the New York City were closed, my wife went to a colleague’s house and stayed there until three days later when was able to return to our home.

Once satisfied that my wife was safe but still in a state of shock, I went to a nearby square and sat on a bench watching people hurrying to the scene. That state of shock was with me, like with many other New Yorkers, for at least three months after the attacks. During that time we could smell the pungent odor of burned materials, some of which certainly came from the incinerated bodies of thousands who had perished there.

One was Sean Rooney, whose last moments were described by his wife, Beverly Eckert, in a story published in New York magazine in a special issue on September 2011. Beverly described how her husband called her while he was trapped on the 105th floor, unable to find an escape route as the flames approached ominously towards him and how, during his last minutes of life could only manage to say "I love you, I love you." Then when the smoke almost prevented him from speaking, Beverly heard a terrible noise of something cracking, followed by the sound of an avalanche and a groan, probably from her husband when he felt the ground crumbling beneath his feet.

When George W. Bush later visited the scene of the tragedy, Karl Rove, one of his closest advisers, saw a fire truck completely destroyed in place. Rove then asked two firefighters to jump repeatedly on the truck to make sure that it would hold the weight of the U.S. president. When he made sure there would be no problem, Rove suggested to Bush to get on top of the truck with a megaphone and address the firefighters gathered there.

It seems impossible that someone who had been trapped inside the towers could have survived. Yet that is what happened to 20 people, including firefighters and police officers and an administrative secretary of the Port Authority called Genelle Guzman-McMillan.

As Matthew Shaer tells in New York magazine, Genelle followed a group of colleagues to the smoke-filled stairways. As they descended, Genelle was certain that she would survive and could go down and meet with her boyfriend, as they had planned to do. However, she suddenly lost her balance as a result of the collapse of the building and was dragged to the ground floor surrounded by tons of cement and steel. Finally she stopped, and felt something soft and warm under her – it was a dead person. She remained silent for 27 hours, praying and asking God for her life. After that time a German Labrador named Trakr managed to find her.

The shock people experienced as a result of the attacks may mirror the shock that Americans felt after the Japanese attack on Pearl Harbor. Such was the state of fear after the attack on the towers that the noise of the few aircraft that crossed the air afterwards was enough to frighten New Yorkers.

Such fears led to unexpected reactions. A friend, an art teacher at a university in New York, told me recently, talking about that fateful day: "Although I am a total agnostic I must confess that after the attacks I felt something strange, as if my house was invaded by ghosts whose steps I seemed to hear at night. I was so afraid, that I had to ask a Buddhist priest to make an exorcism ceremony of my apartment to feel that I was not going crazy. "

The attacks on the Twin Towers caused the most concentrated response to an emergency in the history of the United States. It is estimated that at least 100 units of emergency and dozens of private ambulances headed toward the scene from which they took the injured to nearby hospitals. At the same time, more than 2,000 police officers searched the towers and rescued survivors. But the weight of the response fell to the Fire Department of New York whose members had a truly heroic response to the events.

Will we be ever be able to eliminate terrorism? Secretary of State Hillary Clinton told the Security Council of the United Nations on September 27, 2010, "Stopping people from becoming terrorists," Clinton said, "requires addressing the political, economic and social conditions that make people vulnerable."

On the 10th anniversary of the tragedy one of the main lessons to be drawn is: Violence begets violence, and intolerance breeds intolerance. Unless there is a new approach to preventing terrorist acts we will continue to live under the threat of preventable terror.

Political confrontation is not the answer. It's easy to create an enemy. It's much harder to understand "the other", a necessary approach if we want to eliminate misunderstandings, while honoring the desire for peace and security of all peoples of the world.

Dr. Cesar Chelala is a co-winner of an Overseas Press Club of America award.