The quote you hear is:
""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, 'I am become Death, the destroyer of worlds.'
I suppose we all thought that one way or another."
It is the voice of J. Robert Oppenheimer, the Berkeley professor who became director of the Manhatten Project to develop an atomic bomb during WW II.
He recalled the verse after witnessing the first nuclear explosion in Alamogordo, New Mexico in July, 1945.