The entire building came down "at once", not suspicious?
What building comes straight down without interruption?
Lest I be reckoned as a fool, you do not want to know what happened, correct? Get this out in the open so the subject can move on, be so kind?
Under what circumstance(s) do buildings fall down?
How many circumstances are there for a building to fall down?
Do buildings fall straight down under any circumstance?