Good question; but why this time, send a message with a tarot card? I've not heard any such thing was done previously in any bombings, domestic or abroad. Why change "tactics" of communication, for our benefit?
"We're working as hard as we can," he said (Moose). "People are continuing to give us information; we're following up those leads. We want people to keep the faith and remember this is certainly not the first person or group of people who tried to change us or change the nation. So please continue to be resilient."
Forgive me if this has already been addressed (I haven't finished reading the thread yet); but I've heard that snipers usually leave behind a "calling card", and that American military snipers usually leave the "ace of spades".
I've, also, heard that we did this when we were in Afghanistan, so the shooter could be a Muslim terrorist with some delusions that he even comes close to being on par with one of our boys.