The selloff came as more than $2.7 trillion worth of options expired, an event which typically spurs heightened volatility.

The Dow dropped 500 points on Friday afternoon as the Justice Department’s investigation into UnitedHealth weighed on the market. Additionally, a weaker-than-expected U.S. housing sales report added to the pressure,

U.S. stocks fell Friday on word of a government investigation into UnitedHealth (UNH) and gloomy economic updates, driving Wall Street's major averages toward losses for the week. The S&P 500 (SP500) was -0.