The first instance of humour of this sort that really stands in my mind was the Aberfan disaster in 1966. If you consider that 144 people were killed (116 of them children) when the coal tip engulfed the school it was not one of the more amusing things that have happened in life.

Within days (hours?) of the disaster there were loads, and I mean, loads of jokes ("What's so good about the Aberfan coal service?" "It delivers right to the door" etc Sorry if it offends anyone it is an example).

Perhaps it is just in the nature of things of how humans deal with such enormous emotions.

Biafra, Irish hunger strikers, Space shuttle, murdered politicians - hard to find any area where such humour does not exist.

Before 9/11 happened there was a webcam on one of the Twin Towers which had some text associated with it something along the lines of 'Watch aeroplanes fly towards you' which I guess is fairly tasteless in retrospect but has a hint of gallows humour about it. I only know this as I tried to access it when the disaster happen just in case it was still working and have a screenshot of it somewhere.