subject line: why does home hurt?

I just got back from three months in Europe.
I had been in Paris when the terrorists took that city’s hope hostage.
I saw the blood in the streets, the tears on the faces, heard the screams of terror coupled with the terse commands sounding from the men behind the guns.
All of this pain, all of this suffering, all of this hurt in the people of Europe, and somehow, being home around all of my friends who have never experienced anything that robbed their safety hurts worse.
I just need someone to explain to me why the pain of false security throbs just as hard as a ripped open city.