Hawking: A.I. 'worst event in the history of civilization'

If all humans were extinguished, then the only organisms left to think 'this is a tragedy' would be the Artificial Intelligence itself. There will be no humans left to lament the loss of human civilisation. The sense of 'tragedy' could only live on in whichever individuals of whatever species are left to survey the wreckage. So it would really only boil down to whichever life form - human or their AI overlords - were more capable of experiencing regret and remorse for the genocide of a competing species. My guess is that any A.I. created will probably be too sophisticated to be speciesist, or to be fearful of death. So in that case, the AI would not feel a sense of tragedy or remorse for the loss of humans, but humans are more likely to perceive the loss of an AI civilisation as a tragedy.