"This matters how?"
This is important because the truth deserves to be heard. I don't know for sure what he did and did not yell but it certainly sounds like that is what he said on the amateur video.
If we don't learn and publicize what contributed to this kids anger that would cause him to "snap" as the authorities described it what are we to do???
If he was learning this from his local mosque or internet chat with his like minded friends I would certainly want to know if it might prevent a future incident like this.
I would imagine that if a man decided to drive off a cliff to kill himself, he would utter the same phrase, if he were Muslim.
I doubt the phrase is exclusive to terrorist scum.