There are some bad, angry, disaffected people in this world who want to cause harm. They come from all over and mostly they believe themselves to be acting out the will of their idea of God. They want to put an end to the sort of liberal freedoms we have enjoyed over the last 50-60 years. Some of them claim to be Muslim, some claim to be Christian. Neither have understood the key message of their religion.
The biggest danger we face is not the terrorist, but the governments who are using these people as a pretext to enslave us.
You are a wise man.