I think they are American soldiers. They die in the war and they return as the undead.
It’s not a virus or anything material that brings them back but their anguish felt over having died in a sensless war. They can speak but it pains them so they only speak when necessary. They can not die even if they try to kill themselves. They walk around in a small town. They try to bring light somehow to how the politicians use war as a tool.
There are 2 brothers in the movie. I think one of them finds the other’s pistol in the house and accidentally shoots himself in the head. Or maybe the zombie brother shoots the living brother.
The Revenant (2009).
Masters of Horror – Homecoming (2005).
Deathdream AKA Dead of Night (1974).