I agree. It's not Satanic. The "Death" card is the obvious card for an unknowledgeable person to leave, but there are 3-4 other cards in the deck that an occultist would probably use in preference to that one.
This really points towards a homegrown nut, probably a teenager or young man, with a passing acquaintance with occult paraphernalia.
Alternatively, this could be a copycat.
Have the "death cards" in Afghanistan been Tarot, or just ordinary playing cards? If the former, this stuff has gone more mainstream than I thought.
In the LEO's frantic quest for this person/s, I would seriously be skeptical of any "evidence" found. It provides that "we are making progress" cover statement, and portrays the person/s responsible as being bizarre. Like doing what he/she/it is doing is not nutty enough? I doubt the shell casing. I doubt the tarrot card. If I were a cop who had a real dislike for someone, all you need is a deck of tarrot cards and a same caliber gun to leave in someones trunk and they will be locked up for quite some time.
The key to finding this person/s is catching them in site scouting before the next round of shootings. The guy in a park looking at views and buildings. The person in the cemetary who is looking at surrounding fields of view. A person looking at parking lot video equipment.(Remember Mrs. Toogood? she was smart enough to look horizontally for witnesses but not vertically)