A similar event occurred on bitcoin-24 during last years april rally (although not simultaneously with an actual 'crash'). In that case, the reason was that someone figured out how to hijack users login sessions, and then proceeded to transfer all their coins all to his own account by placing a buy order in the very thin USD order book and then selling all the coins in the hacked accounts to himself. Perhaps his bid order was too small, but it took the price down all the way to $0.

However, I think Hanlon's razor is appropriate here.
>Never attribute to malice that which is adequately explained by stupidity.

Just a big panicky whale that made a typo in the heat of the moment and bought a very expensive ticket for his spot in bitcoin history.