I looked at the volume from Bloomberg - nothing out of the ordinary. Taking a guess, it looked like the shorts tried something and someone (SYX) rode in to defend it.
These short jerks can start a panic fairly easily because they know the computers will lock in on anything move rapidly moving downward and start selling. The fact that support started at 10% decline is very interesting.
So, maybe that is a trip level in which SYX (the Leeds?) get involved in buy backs. Makes sense.