I would add that given the big sell off going on in the general equity markets around the world, some funds land up with margin calls.  RVX is mostly not marginable for many funds (too illiquid) and so becomes an efficient way to meet margin calls.  

The fact that it was mainly one seller suggests that someone wanted to raise cash.  I don't think you can read anything fundamental into the selling (e.g. "someone knows something" kind of fear).  

I view this as a good buying opportunity.  Seems like a classic bottom...big selling volumes at a temporary low...in front of a big slug of company making data coming through in the next few weeks/months.