I have this habbit, it's almost a condition. If it's not one of those two, then it's still something annoying that i can't refrain to do. It goes like this:
Something really bad happens. You know, a car crash outside happens, tires screeching, metal clashing - and you laugh!
People around you annoy you to hell, you feel alienated from others because they seem so out of touch with your world, seem to be phony, almost unreal. You start to hate them for what they are, for what they do, how they react to you and how they take everything they enjoy for granted, their privileged minds became dull and superficial - and you laugh!
People die. They don't eat, they got nothing to drink. You see the misery some people have to live with, their desperate struggle to survive, you live forth in prosperity, while others die in their own piss - and you laugh!
I have this condition. Bad things happen all the time, sometimes they happen to me - and i laugh!
In closing I'd like to say: Be gentle - because the other ones battle is always harder.