Now this is really interesting! Did you watch this on the charts yourself? I only noticed something was up when the red candle was already quite impressive. Sure enough, /r/bitcoin showed the answer by then.
I was in #mtgox at the time, waiting for the release to be announced. We were all wondering why MtGox was rallying down and at around 620 and falling and then came the release.
I'm sure quite a few others noticed and can verify this.
Maybe it was on their webpage for some minutes before they announced it (in IRC)?
Or some MtGox insider got rich on this move.