Twenty years ago, the United States of America changed. And so did the world.

Terrorists took over four regular airplane flights and used them as weapons against the World Trade Center and the Pentagon, which was the worst attack on American soil since Pearl Harbor. But the heroic actions of the passengers and flight attendants of United Airlines Flight 93 prevented the fourth plane from reaching its intended target.

As we watched an actual national disaster occur, many of us understood for the first time that disaster movies paled in comparison to the real thing. It was surreal and in those first few hours, it was terrifying. We lost a sense of security we had enjoyed for nearly one hundred and fifty years.

I heard the news of the first airplane striking the World Trade Center just after I had dropped off my then-five-year-old son, Adam, to elementary school. I was listening to the radio on the way to work. I remember the radio announcer thought it may have been a charter plane having an accident. But by the time I reached the office, the second plane had hit the other tower and I knew it was deliberate. In my heart, I already knew it was terrorism.

I was a network administrator at an engineering firm then, and we all knew no work was going to get done that day. Like many people, we stood around the office television in the main lobby and watched the unfolding news. What was strange to me was hearing the engineers explain the effects of the burning plane fuel destroying the support structures of the buildings, which they believed led to their collapse. It made sense but there was an intellectual disconnect in the way they spoke compared to the fear and amazement I could sense from them.

We were all in shock.

I remember my wife calling me after the second tower collapsed. She was at home with our then-two-year-old-son, Jonavinne. I did my best to comfort her.

The schools let out early that day, so I left work and went to pick up my son and take him home. Then I did one of the hardest things I’d ever had to do as a parent: I explained to Adam, in kid-friendly terms, what had happened in these terror attacks. I had to pray before speaking with him and the Lord blessed me with words. I let him know it was real, it was serious. Many people had been hurt and many people had died. Explaining death was probably the most difficult part. But he received it all from me. To the best of his ability, he understood.

All through the rest of the day, like so many others, we watched the news and the constant replay of the images. It was entrancing, morbid and terrible. My wife and I said many prayers that day — for the victims, the survivors, their families, America, the world, and for ourselves and our family.

But we saw something else start to occur in the news coverage. People were coming together for candlelight vigils in support of the victims, survivors and their families. They were placing flowers and wreaths, pictures of the victims in memorium. And by the next day, a sense of nationwide unity had emerged. Videos of support emerged, statements from many world leaders, interviews with ordinary people from many nations.

Also, amazing stories surfaced from survivors of the World Trade Center towers. Jews and Muslims had helped save one another. People of all races and ages sacrificed to make sure others made it out alive. We heard about the herculean efforts from all the first responders and learned of so many of their selfless accomplishments and sacrifices.

When it mattered, during a crisis, Americans put aside their differences and came together as a nation. In our darkest hour to date, America shined. And like many other Americans, I was proud of us. That togetherness, that shared identity as Americans, helped us cope and survive as a country. It was an outstanding example to the world.

It’s an example we can still learn from.