Their story, which doesn't seem to appear in the responses in that Twitter thread, was that a 2 year old account that only posted once previously in its history suddenly activated, posted a picture of someone holding a threatening letter of some type outside of someone's home, then this was screencapped on Twitter a short time later (~15 minutes). The post was removed 2 minutes after it hit Twitter by the submitter (they originally thought their mods did it, but corrected this, saying it was removed with the note "retarded").

I don't ever read that site other than to look at stuff like this when it hits the news, so I don't claim to know anything more than that, but you were for a time able to look at the forum threads and see the posts they mentioned, etc.