Obviously they were top secret developments. But did Hiroshima and Nagasaki shock the the people in the world, both in the US and in the world? Were there rumours prior to 1945 that this development was going on?
Separate but related:
Did the atomic bombs being used lead to a prolonged intellectual rumination on the creation of the ability to wipe ourselves out? or was there speculative thought before 1945 that we would create this ability, and the ramifications of it?
There was a post that asked a similar question a while ago where /u/restricteddata 's response was (to paraphrase) that it would be a bit like if Obama got on TV tomorrow and announced that the US had successfully tested a spacecraft with a warp drive. Most people are familiar with the idea of warp drive in kind of an abstract way, and the more scientifically minded might be aware of the problems with such an idea and potential solutions to those problems, but it would be shocking to anyone not directly involved with the project if someone actually built such a thing today.
There was certainly a lot of thought about the world changing potential of such a bomb. Robert Oppenheimer famously said that witnessing the trinity test first hand made him recall that bit from the Bhagavad Gita "Now I am become death, the destroyer of worlds.". Richard Feynman, another physicist who worked on the bomb remarked that for years afterwards he'd look at people building a bridge or a skyscraper and think "What's the use?". Leo Szilárd, another physicist involved in the Manhattan Project was also deeply concerned about the destructive potential of the bomb and discussed ideas that would become the basis for "end of the world" popular fiction like On The Beach and Dr. Strangelove.
At the same time, I think it's important to understand how different our understanding of these events are from someone who was actually living in them. From a 21st century perspective it makes a lot of sense to see Hiroshima and Nagasaki as this break with the past where all the rules changed. However, someone who was old enough to be in a position to make important decisions in 1945 would probably have been growing up at a time when horses were still an important part of military life, and bolt action rifles were practically the stuff of science fiction. From the perspective of someone born 20 years after the end of the civil war who lived through WWI and WWII, it's not hard to see the atomic bomb as being another step down the road they'd been on their whole lives.