Technology can actually embed low level sounds in digital transmissions.  Sounds sound familiar to words your mind can make a normal word. :-).  Mad lib syndrome.  Or he needed help. 
I ask this.  Is it possible he heard something?
And is he part of a larger pattern of a problem?
Had anyone in his unit experienced similar things?  In their home lives or work environment?
Would there possibly be anything sensitive or any skills, information, or contacts that he had access to or possessed?
In essence could he be telling the truth?