The year 1999 is when the Earth was invaded by a planet of Wrestlers determined to regain the title of Galactic Champion of the Universe! How did this happen? Easy, years earlier an idiot Earth wrestler declared himself the champion and fueled an interstellar war.
The killer is revealed in the Heroes in Crisis #8 storyline. What the hell is writer Tom King thinking?! This is not the best move for DC Comics to make with this series. Be warned, lots of spoilers here!