What big thing happened in Hiroshima?
The first atomic bomb was detonated on the city of Hiroshima, Japan
The answer is yes but now people are making histories about the atomic bombing of Hiroshima. They made these videos are basically true, not lying. The people in Japan told stories what really happened in Hiroshima a long time ago. People did not video tape the video, they remembered what really happened in Hiroshima.
We can never observe what happened before the Big Bang, if there were such a notion. Not only can't we observe what happened before the Big Bang, but it's even worse than that. The Big Bang was not only the beginning of space, it was also the beginning of time. So there's no such thing as "before" it.