Corpse Creek, 1883. The darkness of the midnight sky was interrupted by bright green light, shortly after flaming stones came raining down on this otherwise quiet town. People stormed out of their homes to see what was going on. The sky was lit brightly green. After a few seconds the first of those meteorites reached the ground with a massive bang.
The people who survived the incident took their loved ones to the Corpse Creek graveyard the next day. The bodies are just underground and the local preacher Noah just spoke his last blessing words to end the ceremony when the ground started moving and a hand reached out of one of the graves.
People quickly pulled their firearms but weren't able to fight back what was attacking them - their loved ones just raised from their graves, one after another. They are not human anymore, people called them "lost souls".