I don't understand

I don't understand how someone can feel so strongly about something that they don't mind killing themselves to injure others to illustrate their point of view. In a way, I am envious that they have found their passion in life. I know I am not that passionate about anything! Then I start thinking did they really know the true consequenses of the situation they were about to create? Did they make this final decision on their own or did someone influence them? How do you influence someone to that extent? How do you make someone believe in your own beliefs? I was talking to my sister and she said she watched a documentary where someone was about to blow themselves up and that person was in constant contact with the so called leaders of the group. The leaders kept up a constant vigil, telling the suicide bomber how he will be going to Allah, how he will be granted heaven and all its heavenly goodies, how what he is doing is what Allah calls for him to do etc. Its as if they don't want to give him time to think something else. No chance of getting cold feet when someone is constantly telling you something other than what your conscious might try to prevent you from doing. I hate all the violence in the world.