Since terrorist organizations have goals and political objectives, it doesn't accomplish much to conduct a terrorist attack without it being linked to the organization. And, in this case, the "calling card" clearly seems to point away from any Islamic connection.
Of course, we can't rule anything out until a suspect is apprehended, preferably in possession of the rifle, and linked to the shootings.
I do hope that our killer isn't too much into Tarot cards. Otherwise, he might seek out a priest as one of his next targets.
Leaving the card was a big mistake. It's a huge piece of evidence that can be linked in several ways back to the shooter. That means our killer is less intelligent than I first believed. Or his judgment is getting impaired.
This is definitely the first break in this case.