Although no one yet knows the identity or nature of the culprits, the international markets not only have determined the culprits but have acted on that perception, as global markets suffer major wallops. The US markets are indicated to open down hundreds of points. An exogenous event of this type has the potential to exacerbate an already weak market. There exists the possibility, however, that US markets could rebound from intra-day lows. Consider the action appropriate for your portfolio, while keeping in mind your objectives, tolerance for risk, and time frame.
Best wishes to all.