It was described in the media as a can of chewing tobacco, but I'm told that chewing tobacco doesn't come in cans, that it must have been either snuff or smokeless tobacco.
My inference is that the tobacco can may have contained the powder with the Star of David, because it's hard to imagine how else the Star of David could have been "buried" in powder, otherwise. The symbolism of a Star of David buried in powder, used to deliver an anthrax attack, would be obvious. A pun on "snuff" sounds a bit sophisticated for a non-native speaker, although it would also make sense, of course.