That "someone" was an investigator for the Air Force (or at least passed as one to the FBI). The document doesn't say the FBI decided it was a matter not worth pursuing, only that the one agent didn't "attempt further evaluation".

It's a curious document for sure.

The American Southwest is the most heavily atomic-bombed place in the world. There was a lot of radiation in the air back then.

Marsh, do you believe that little people in shiny pants came here in saucers?

I find myself enjoying the ambiguity more than either of the alternatives. :-)

Ok, but to what extent do you have to entertain little saucer pilots in shiny pants in order to take this particular document seriously? :)

Oh probably not at all. That's just one of a hundred explanations of wildly varying degrees of plausibility and they're all interesting.

I can just imagine the FBI field agent wiping away the tears of laughter as he types up this memo back to headquarters after chatting with the USAF guys using spatulas to scrape the fried chimpanzees in silver lame' flightsuits off the wreckage of some top secret atomic-powered X-plane.