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 68 of the 77 incoming nuclear warheads. The note states otherwise. This was most likely done to exaggerate his accomplishments as much of the obituary is written with a high and mighty attitude.
 * The obituary seems to have been a rough draft. The end has a note stating that it needs to be updated before then insulting everyone who will end up reading it by calling them illiterate ingrates.

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."