Yes, in 1925 he addressed his experience as "At that moment..." He had a peak experience - which is not all that uncommon. I've had several myself over the years. What is uncommon is his direct experience of the effects and after-effects of a man-made destructive martial power the level of which, until then, he could not have fathomed.
I grew up as a little kid in the 60's. The threat for us wasn't someone with a knife, or a sword, or a gun. It was from something that was going to cause a flash in the sky and instantly fry everything thing within that region of the country. Consequently, I and the others around my age grew up as pretty chilled out people.
Peace, on a larger scale, since WWII, was not been achieved by the sword, but by the atomic bomb.
Well, there's been quite a lot or war since WWII, atomic bomb or not. Anyway, my point was that he talked quite a bit about peace before the war and the bomb - I think that's pretty hard to make the case for a 180 degree shift in his thinking after or as a result of Hiroshima/Nagasaki.