Don't you get it? he actually did type those messages - but it was a prank by the pages. they lured him into it. so he resigned because he actually did it.
The part about luring him into it was somewhat obvious to me based on the responses from the page. I don't think "prank" cuts it. Nor do a think it was a mistake that they got into the "wrong" hands. JMHO, of course.