The video that was put out by this 'anon' is not the standard one. I suspect this could be a attempt to co opt the 'movement' and taint it with anon. But the ace in the hole in the video and other symbols are not the standard ones that he group has established. It simply could be a inside joke for some, or something else entirely.
On FB I see posts about multiple shooters, a United Way fundraiser for Sandy hook on 12/11 and stuff.
12/11 was 3 days before it happened.