A bomb? Are you kidding me?

I'm amazed about people's lack of consciousness. Yesterday we were in our Language class discussing some issues, and a man entered the room saying that we had to leave the building. They had received a message saying that there was a bomb in our school.
WHAT THE HELL THE TWISTED MIND WHO CALLED WAS THINKING WHEN IT DID SUCH STUPID THING??????
Once more, I proved myself to be a balanced person when something goes wrong. But when I was at home, after kissing my son, who was already sleeping, I started shivering, and my heart wanted to jump out from my chest in despair.
I have to recognize that at the moment in which we were asked to leave the building, I only cared for one of my closest friends to be calmed. I didn't want to loose her in the crowd, because I knew that she was shocked.
This was the first time in my 28 years in which something like this happens to me. Of course I have heard many times about practical jokes like this, which were done in some institutions. However, since we are among adults, I couldn't believe people's stupidity. The news of a bomb threat came to us when the building was almost empty. We are in a wing which is almost forgotten. So, if the bomb really existed, I wouldn't be here writing at this moment.
I wonder how can someone be as careless as to threat people in this way.
When I decided to start writing about this, I was quite upset, my nose was bleeding out of rage. I couldn't understand anything. I was too upset to think in my own health. I felt impotence at its highest rate, I wanted to find someone responsible for all this, and punch his or her in the face.
Now I'm calmer. However, I still cannot understand the situation, and this is not good for me. I always look for understanding everything, even when I do not accept it... I need to understand, I need a rational answer for everything that happens (or not) to me and to the ones I care for.
Does anyone have an answer? I would be quite thankful if someone explains all this in a reasonable way.