Didn't catch his age...if he was younger than his 40s (probably, today's 60s) I'd probably lean toward some infection ("camp fevers") or head injury. I gather the high cholesterol/artherosclerotic plaques is more of an "age" thing. Expect it's one of those things we'll never know without an autopsy or some modern...ala "CSI"...post mortum. Assume he's buried at the prison camp site? Was it a mass grave or did they at least get the dignity of individual burial?