Since the mention of "A SINGLE CASING" was so noticeable, I thought it might be a souvenir of a sort. AFTER, the sniper shootings, I thought it might be the sniper's "remember me" souvenir to one of his Muslim, USA hating friends.
And when we get one, we usually wind up with more than one. Let's see what happens here. Someone is on the ball to look for this guy in the first place.