Hmmm.
More plausible, but still unlikely. To work on computers in the military, you must have at least a Secret level clearance (it's a job requirement for the MOS feild). Which means our enterprising young tech must have had at least one securoty breifing (they're required periodically to maintain clearance) and thus would have known what he was supposed to do regarding secure documents.
Thus, he has admitted to violating a direct (standing) order, violating his security clearance, overlooking a security violation (not sure what the official term for this would be), and now, since he's talking about it, violation of his security agreement and, possibly, treason (assuming all this is true). And he can't even plead ignorance...if his story is true, he knows (or should have known) the procedures for secure documents.
However, again, I find it highly unlikely that a person without a Top Secret clearance would be allowed to work in an area where TS documents were stored, without being granted that same clearance level. Does Chavez claim he had a TS clearance?