As a funny note, there was a few users who spread the rumor that the one dumping the 69K that triggered the crash was Silk Road (for example, see:
https://bitcointalksearch.org/topic/m.1804571)
The dump was real, the one who did it's unknown (at least I have seen no proof other than rumors and different posts).
And of course a dump triggered the crash - it always start like that. The BTC is so ridiculously illiquid that a tiny dump of +10.000
BTC would trigger a panic selling and a huge crash. Heck, a 200K
BTC dump would take us to low single digits! That gives you the idea of how easy would be for a BTC enemy with not-so-deep pockets to destabilize BTC.
And now imagine that an old miner decides to dump +500K
BTC coins because it's time to be rich, and he doesn't give a fuck