I’ve just started looking into archived versions of the columbinegame.com/discuss forum (this is where the “Shocked Beyond Belief” forum was located originally, when the Sandy Hook shooter started using it.) The cache is very sparse, but I did find this link to a thread started by “Smiggles” from March 2010, titled “Comprehensive list of mass murderers and their attributes”:
…unfortunately, like most of the Wayback Machine’s cache of the forum, the linked topic is missing. However, we can still deduce a few things based just on the title and timing of the thread:
1. He shared his “catalog of mass murderers” with others.
2. Thus, Smiggle’s later reference to it in this thread was a call-back, not a hint:
3. He was posting as early as March 2010 (the previous “oldest thread” found was from April). Although the date on the far-right is when the most recent reply was posted by another user, further down the page you can see that Smiggles started another thread, “Sam Brown? (The Killing of America)” (also a dead link) which shows no replies; so the timestamp “Thu Mar 11, 2010 1:49 am” was indeed when Smiggles started that thread.
Also, the Smiggles profile page at this version of the forum shows that he posted at least 353 times, as opposed to the 296 listed at ShockedBeyondBelief (thanks to reader Joachim for pointing this out):