EVENTS LEADING UP TO THE APOCALYPSE could possibly be explained in a possible series of books by Tyree Darnell Tillman Junior. The events are not easy to explain but lets do it.
Explanation #1: The fire that still burns under the ground of Centralia, Pennsylvania suffers a terrifying rage of series of ashes and burning. The fire somehow escapes the area that was shut down and escapes into three mile island there where one of the nuclear reactors has a supermassive explosion. Releasing radiation into the air, but with the combination of the fire and let's so want if all the reactors were not shut down completely like in Chernobyl 1986 and underwent n overheat and released an unknown virus into the air causing metal detoxictity . The state of Pennsylvania orders State of Emergency and quarantines the whole state. However the next few months, the victims that survived the incident die in strange and undivided ways, , after bury that somehow rise from their grave while a news reporter snaps photos of various graves of his ancestors, one of the rises from the grave behind, he snaps one last photo, takes a glane at it and notices something behind him, he turns around no ones there he puts the photo in his pocket and turns around and the walker bites him dead in the throat and tears his throat. He gets away but runs into more walkers, he makes in attempt to run toward the exit but the walkers then doublback and start eating him alive riping flesh from his bones, his blood splatting on his glasses.