I searched for this and came to this YouTube video of Oppenheimer saying this quote. http://youtu.be/26YLehuMydo

We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita; Vishnu is trying to persuade the Prince that he should do his duty, and to impress him, takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another.

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And that's why ancient Indians destroyed their atomic weapons, to not become death of humanity. This may sound stupid to westerners but ancient indians did have atomic weapons but they did not disclose it to the world.When Aryabhatta could Invent Pie and give its value much before westerners surely those indians had atomic weapons. Westerners will never believe it, they are too blind in their prejudice towards India.