A Tragedy Has Befallen All Mankind

 is a paper note obituary in Fallout: New Vegas. It is automatically given to the Courier after killing Mr. House in the Lucky 38 casino's control room at any time.

Trivia
In the FNV storyline, Mr. House's defense systems defeated only 70 of the 77 incoming nuclear warheads. The note states otherwise.

Behind the scenes
The note pays homage to Vladimir Nabokov's novel Lolita by saying "House was orphaned at an early age when his parents died in a freak accident (auto gyro, lightning)." In Lolita, the main character Humbert nonchalantly mentions the death of his mother by saying "My very photogenic mother died in a freak accident (picnic, lightning) when I was three."