
Whatcha going to do now? All I knows, is that I've got my rifle and my crowbar ready! I do appreciate their use of "caution" instead of "Run You Mother Truckers!" (Maybe that's why many people still don't believe the message - it wasn't urgent enough or Samuel L. Jackson enough).
And just incase you didn't understand the first construction sign message, the hackers were nice enough to send this message too:

Pride is a terrible thing to waste, so stop being mad because you didn't see it coming. Don't be angry because I was right (like always). Haters have tasty brains - so you better stop hatin' or the zombies will get you first.