“I think Gricar feared being exposed as a customer and made himself vanish.
He was determined to hide his personal computer and destroy the hard drive... compromising photos or child porn?”
Considering the facts this may be more plausible than my suspicion that he kept digging after the decision to not prosecute in 1998 and hit upon some of the richer people involved. It is scary easy to make someone disappear. Especially if the person is rich and has everything to lose. The risk of not getting rid of the guy is greater than the risk of getting caught making him disappear.
From Wikipedia:
In April 2009 Bellefonte police revealed that before his disappearance, Gricar used his home computer to perform internet searches on topics such as “how to wreck a hard drive”, “how to fry a hard drive”, and “water damage to a notebook computer”.[14]
http://en.wikipedia.org/wiki/Ray_Gricar