The City lights blinked out forever--literally overnight--with a sudden finality that caught even the most nuclear-winter-prepared/Guns N Ammo reading/Campbell's canned soup and distilled-water stocked/backyard-fallout-shelter-owning-survivalists completely off guard. Armageddon had always been there, sleeping just beyond the horizon line of our periphery, but it awoke fully clothed and ready to go to work that day.
It was an ordinary Thursday, just like any other. The MUNI lines were choked as always with angry elderly women clutching plastic shopping bags full of pungent vegetables, poultry, and recyclables as if their lives depended upon the contents of those bags (maybe they did) and the usual gaggle of gibberish-mumbling crazies talking to themselves with cellphones plugged into their brains, some without. 
That day, baristas were 5 minutes, 23 seconds late for work on a city-wide average. Bartenders were making their rent in tips as rowdy soccer fans converged in their local Sunset, Richmond, Mission and SOMA district faux-Irish pubs to watch the latest big championship match between Ireland and...some other country.
By Saturday, less than two days later, the desperate siren-blare of emergency vehicles, the insect hum of DPT tri-bikes carrying cutthroat ninja-sneaky meter maids ready to make their weekly quotas by slipping bogus $55 parking tickets under the windshield-wiper of your best friend's beat-up, barely-working mid-90s Mazda you were borrowing just for the night, and the cloud-cutting rotary-whine of channel 5 news traffic-report helicopters chopping through the sky had been silenced forever.  
As if sensing the absence of gardeners, street sweepers and garbage men, weeds grew out of the cracks of the streets and sidewalks with the newfound urgency of a wildfire. Leaves swirled through glass and concrete skyscraper canyons, settled, and slowly began forming mounds as if attempting to fill the spaces that angry elderly women with plastic shopping bags, cellphone schizophrenics, and drunken soccer fanatics had once occupied.
Speculation about how the End of the World would actually occur had always been a theological reference point for religious zealots hell-bent on giving the Book of Revelations some validity, but had taken on a tone of comical absurdity in the hands of post-Y2K pop culture and disaster movies. A horde of zombies rising from their graves and feeding on the flesh of small bands of living human survivors was one of the more popular, albeit fantastic, apocalyptic theories. Some predicted that robots would enslave us, some thought aliens would invade us, while still others--baring signs reading "THE END DRAWTH NIGH," arms stretched meaninglessly up towards the hollow heavens in the sky above--believed biological or nuclear warfare to be the most likely form of humanity's demise.
But by the following Thursday, speculation had become a moot point; none of it had mattered at all in the end as the power-grid of the City, and then human civilization altogether, had been suddenly switched off for the last time by an alcoholic rent-a-god, leaving the face of the globe devoid of any trace of the spiderweb-night-glow of terrestrial city-lights. 
Only the birds in the sky and the fish in the sea were spared to fill the blank pages of history that were to follow human(kind's) fading footprints.

*

Aeons later...
When those birds learned to read, they would see cryptic symbols inside a crooked heart jaggedly carved into a tree trunk surrounded by a mote of fallen leaves and ragged newspaper pages blowing through the streets like tumbleweeds.
Aeons later...
Those tree-scratched symbols would form the sacred commandments of a secret new religion built upon the ashen, worm-eaten remains of two skeletons holding hands and a ****** trail of broken hearts trailing from their ribcages into the worm-mouths of babes.