In New York at the Exchange, crash occured at 2:40 May 6. Looking into DJIA's intra-day chart,the index penetrated the support line from upper side to down side at 2:30, then the index downed more than 600 points.
I think there are system trading behind this typical behavior.
U.S. investment houses are playing simple games in a way. Don't you think it is interesting for you? Why don't you study the basic chart of the stock together? ==(Hiro Une,TEIC2 ltd)