RE: 400 out of nearly a million is, to borrow an accounting term, non-material.
I guess, with this 3000 dead in 9/11 is to borrow an accounting term, non-material compared to 300 million Americans.
That was an act of war. The war part makes it material. Acts of suicide are a different scale. An insignificant percentage of people dying from their own actions does not make a crisis.