That is so common, even the eco-weirds have used that symbol.
It seems pretty juvenile. Now the "and some other symbols" might
be interesting.
Sorry, had to come back for this. I had one of those odd "moments of clarity" that I get after a bad headache goes away.
I remembered the roots of the "grim reaper".
It certainly may be juvenile, but historically, it's something else. I'm reminded of how thoroughly versed OBL is in world history. It's certainly more obscure than the Westfalia treaty, but not because of anything other than the story is about 400 years older, and it started just before the dark ages. It's with this in mind that I'll take it seriously for a few minutes, knowing that airports are the most effective way to spread bio agents.
This may be entirely off the wall, but I'd be remiss not to bring it up as it deals with bioterrorism, or at least one of the first "stories" of bioterrorism.
I may be off on a few details, but I'm not prepared to search right now, so here goes:
There are records of witness statements from a variety of places around europe that involve the sighting of men dressed in black, wearing strange clothing with hoods and masks, and carrying strange devices that resembled "brooms" or ""scythes". It was reported that these men would show up out of nowhere, and "sweep" the fields and roads, disappearing almost as quickly as they arrived. All of this was immediately prior to the massive "breakout" of the plague. It was believed then that these "black men" started the plague.
We can lay the spread of the plague at the feet of the inquisition, because cats were killed for being demonic, leaving the rats with few enemies and allowing them to reproduce rapidly. That's a whole other story, but there are those of us who believe that one hand has been behind most everything of this type for the last 2000 years.
Anyway, over time, these "black men" evolved into the "grim reaper" as we know it today.
My point is this: If the letters are valid, it's only because these guys are educated that they're using the grim reaper. If that's the case, then they are possibly tipping their hand as to the type of attack. Unfortunately, that type of attack would be most effective at the very places where they mailed the letters.
Black Wind.