The link also has a photo of the terrorist note that someone else may be able to post.
Indexing.
Some experts are saying that the words "Allah is Great" are meant to lead investigators astray by making it look as though Muslims are involved, even though they aren't. The experts say that Muslims would not have drawn attention to themselves and their deed by including these words.
I think those experts are wrong. The Muslims seem to find it superstitiously necessary to call on Allah at the time they are attacking someone. I think they would have made sure to include these words so that they would be read at the time the letter was opened and "the attack" actually took place.