New York has not been the same since the events of 11 September 2001. It took several years for the city to regain its previous energy and vitality. Twenty years after that dreadful day, the echoes of the tragedy persist.

A fateful day

I remember vividly the terrible day when our lives – and our world – changed forever. I was listening to the radio in my apartment, a few blocks from Ground Zero, when the plane hit the first tower. I could hear 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 a.m. 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, there would be no more attacks on the towers after the second plane hit. Without fully understanding the significance of the events, I felt that a relatively peaceful way of life had been replaced by a darker, more sinister one.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 death rather than remain trapped inside an inferno. Richard Drew, who photographed one of the iconic images of that fateful day The Falling Man, the lonely image of a man falling to his death with one of the towers in the background, said recently that for him it was the image of the Unknown Soldier. An estimated seven percent of those killed in the attack on 11 September did so by jumping into the void from their offices. We also learned of the heroic behavior of hundreds of firefighters who risked their lives and of the many other people who lost theirs. One of the firefighters was a 34 year old Argentine by the name of Sergio Villanueva. That day, about an hour before the attack on the Twin Towers, he had finished his shift. But, as on so many other days, he had stayed behind to have breakfast with his colleagues. When he heard news of the attack, he decided to join his fellow squad members and went with them to the towers to aid the rescue efforts. Neither he nor his fellow brigade members ever returned.

We also heard heartbreaking stories about people we knew who were killed that day. One, the son of friends, had just enough time to call his brother and say "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 had 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 desk and died when the fire ravaged his office.

What promised to be a peaceful September morning turned into a nightmare. As usual, that day – a beautiful day with a diaphanous sky – my wife and I woke up at about 7a.m. We had breakfast and she left for work on Long Island, about 45 minutes from home. I was planning to have a working lunch at the United Nations headquarters.

Lack of communication

After the second attack on the towers, I tried to contact my wife at work. It was impossible to communicate with her by phone. I learned, however, that I could call the Borough of Queens, where a medical colleague, Dr. Juan Rivolta, lived. I wanted to see if I could communicate with my wife with his assistance. I summarized what had happened. He thought I was joking but changed his attitude when he heard the desperation in my voice and was finally convinced when I told him to turn on the TV.

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, so they turned on the TV and were able to witness the horror of the events taking place. Since virtually all roads leading to New York City were closed, my wife stayed at a colleague’s house for the next three days. Satisfied that my wife was safe, while I was 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 stuck with me, as with many other New Yorkers, for months after the attacks. We could smell the pungent odor of burned materials, some of which certainly came from the incinerated bodies of the thousands of people who had perished there. One was Sean Rooney, whose last moments were described by his wife, Beverly Eckert. He had called her from the 105th floor as he was unable to find an escape route. The flames were approaching ominously and, during his last minutes of life, he only managed to say "I love you, I love you." Then, when the smoke prevented him from speaking, Beverly heard the terrible noise of something cracking, followed by the sound of an avalanche and a groan.

A life-saving dog

It seems impossible that anyone trapped inside the towers could have survived. Yet that is what happened to 20 people, including some firefighters, police officers and an administrative secretary of the Port Authority, Genelle Guzman-McMillan. As Matthew Shaer reports in New York magazine, Genelle followed a group of colleagues to the smoke-filled stairway. As they descended, Genelle was certain that she would survive and could go down and meet her boyfriend as they had planned. However, when the building collapsed, she suddenly lost her balance 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. Eventually a German Labrador named Trakr found her.

The shock people experienced as a result of the attacks perhaps mirrored the shock that Americans felt after the Japanese attack on Pearl Harbor. Such was the state of fear, that the noise of aircraft crossing the sky 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, "Although I am a total agnostic, I must confess that after the attacks I felt something strange, as if my house had been invaded by ghosts whose steps I seemed to hear at night. I was so frightened that I asked a Buddhist priest to exorcize my apartment and assure me that I was not going crazy."

A heroic response

The attacks on the Twin Towers produced the most concentrated response to an emergency in the history of the United States. It is estimated that at least 100 emergency units and dozens of private ambulances headed to the scene to pick up the wounded and take them 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 New York City Fire Department, whose response to the events was truly heroic.

Will we ever be able to eliminate terrorism? Twenty years after the attack on the World Trade Center towers, terrorist groups, such as Isis-K, still exist and cast a dark shadow over the world. One of the lessons to be drawn from that tragedy is that 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 terror. Confrontation is not the answer. While it is easy to create enemies, it is much harder to understand the “other" – a necessary approach if we wish to eliminate conflict and to honor everybody in the world’s desire for peace and security.