Since he is a vet of WW II, and served during hostilities, even if he wasn't a citizen it should be easy to get his papers done: relevant link. I served with several non-American citizens in the military (including one Russian fellow, which was kinda ironic in the early Nineties) Serving in the US military is a time-honored way to get citizenship.
I read the article a couple of days ago, man should get his papers, the fact that they threathened his social security....shame on them.