Dropping the Bomb in Hiroshima and Nagasaki?

Question:

When the US was about to do that did we mean to drop it during night to reduce civilian casualties? But then Japan intercepted us before we could?

Answer:

I don't see how dropping bombs at night would reduce civilian causalities. In fact, it would probably increase them.

The plain fact is, the United States didn't care for the number of causalities: they needed the war to be over as soon as possible AND demonstrate other countries (including 'allies' such as Soviet Union) their newly acquired might. That hundreds of thousands of innocent people would die in the process was of little consideration; after all, the Japanese did bomb Pearl Harbour with little regard to innocent lives lost there.

EDIT: If everyone is asleep, they have no chance to escape. Ergo, there are more causalities.
As for dropping the bombs on the production buildings:
a) it's a lie; the pilots didn't care much where they dropped the bombs, nor did they need to.
b) whatever building they dropped the bombs on, how would it matter? Those were atomic bombs, not ordinary ones: they killed everyone within miles.