In the guide Phil mentioned one of his sources said Marines don't go AWOL, they go UA (unauthorized absence).
Things may have changed between Vietnam and when I served but it's my understanding that these terms are defined by time: UA is up to 30 days someone can be gone and AWOL is over 30 days.
Maybe I missed something but why did the guy working at the diner not get targeted as well? Two of the three were doctors on the project, but the second person who died was a regular Marine; wasn't everyone involved being "cleansed"?