I'm not yet sure if this is ongoing downside follow though (weakness), or some sort of gap down shakeout.
The overnight futures often do the opposite to what happens once the market actually opens, however if there is really serious strength or weakness shown during the overnight session, it may be a true representation of market sentiment.
All the US Indicies have open gaps below (at various levels on each), so those gaps maybe closed as price comes back.
There has been plenty of talk about those gaps, and their closure sometimes becomes self fulfilling......