Books

I come back from a long vacation, during it I read a book that want to talk about
The subject is a plane couth by terrorists, what I learned from it is that they think different because they grow up in a world where you have to kill for living, or there maybe another explanation, that they just can not find what the sense of life is, and decided that life has no sense at all.
What do you think? I just try to understand better what causes such an attitude towards life and death.