These words are a paraphrase of Bhagavad Gita 11:32. This quote was from the now-famous scientist who built the weapon which tore apart the very fabric of weaponization and warfare.
Such regret can be inferred from these words, as felt by its own creator. If I were the one to make the decision to drop the atomic bomb, I would never do it because it was a very deadly weapon that not only killed thousands of people but also destroyed land and property.
Many people lost their family, friends, and homes, and even after so many years, the drastic effects of the radiation persist. To oppose Japanese tyranny in the southeastern countries and to bring an abrupt end to the world war, such an excuse was used to satiate their revenge and to redeem their hurt ego. Morality was thrown aside by such insidious and malevolent intent fueled by fear and rage.
The fruits of the war were not to be borne by the people for the sickening acts of the militants. They could have solved the situation by building friendly relationships with each other and in many other ways, but dropping a deadly bomb was not necessary.
Pestalozzi Children's Village Society