This will be using the Shadowrun system, but not be a Shadow Run game by standard senses. The game will be set in the modern day world, and all news in the real world will be valid up until the start of the game. Then, as the title says, things will go wrong, very very wrong.
In short order the world will change from advancing modern age to Life after Apocalypse. Many things will have gone wrong. It wont be one simple cause, but a combination of events any one of which the nation, the world, could have handled. However this tips the scales. Quickly expect the land to go from 6bilion people to say 60 milion, maybe less. Do the math and look around you. If thats the high end estimate if you can count 99 people around you hope that your the one that lives.
At the moment there is one group slated to play. In all fairness they asked for a solo game, but with their approval I am searching for some othe groups. No groups will start near one another, nor can any group be more then three people.
Also keep in mind that these people are real world mundanes. No Magic, no true cyberware, no meta humanity. There is potential for all these things, but for now? Nope. So please either try to make yourself, or use a real person as a model when creating a character. A CIA specialist who has marine, seal and ranger training and .... ect will likely be overlooked in favor of a car mechanic or a IT specalist.