Why do we laugh when we shouldn't?!

Why do we laugh when we shouldn't?

My father checked four of us into a cheap hostel during a ski vacation, and we all slept in bunk beds. But, the lower bunk (where my father slept), did not have very much space between him and the upper bunk, (where I was sleeping), and throughout the night I kept hearing my father bumping his head on the lower bunk.
Finally around 5 AM, while it was still dark, he bumped again, but this time, after a short pause, we heard, "Oh God Damn it!!!, as he hopped out of bed and was in the bathroom looking at a cut on is forehead.. Just a minor cut, but probably left a scar, and he just kept carrying on.
Meanwhile he turned on all the lights and ordered us all to get up, and then went back into the bathroom, carrying on again, "oh Goddamnit,.. Oh Goddamnit!
Finally, I snorted, and then I heard this yell coming from the bathroom, "You think it's funny don't you?!!!"

I replied, "No, I have a cold!" (lied).
I didn't really "think it was funny", but I laughed.. Why did I do that?

1 week ago
Sure he's OK now,
Like I said, it was just a little cut. I'm sorry that happened and I don't delight in others' misfortunes, but the way he carried on in reaction to it, was what made it seem funny to me.
If his wound had been really serious, he probably would have fled the scene, and been in the emergency room getting stitches, long before any of us had woken up...
Then, of course, there would have been nothing to laugh about at all, particularly three lost kids looking at the hotel bill by ourselves. That would be nothing to snicker at.

Its a common reaction for some people to laugh when a situation is really serious or awkward or confusing, not just when its funny. Its kind of a defence mechanism. And from the way your dad was carrying on (waking you guys up and all), I would've been confused if not a little scared. I don't know why it happens but I think it has something to do with people not knowing how to handle some situations. So they just laugh. :)