UnitedHealth Group Incorporated stock drops after a rare earnings miss and CEO resignation. Click for the impact and potential buying opportunity in UNH at $335.

U.S. equities were mixed at midday, with tech shares and a better-than-expected consumer inflation report lifting the S&P 500 and Nasdaq.

May 13 (UPI) -- UnitedHealth Group announced Tuesday CEO Andrew Witty will step down, citing "personal reasons." Witty will leave the role of CEO and be replaced by Stephen J. Hemsley, effective immediately.

UnitedHealth Group CEO Stephen Hemsley, returning to run the healthcare giant after Andrew Witty resigned, said he has the right strategy in place “for the era ahead.”

UnitedHealth Group surprises investors with what its CEO said was an "unusual and unacceptable" quarterly earnings miss, and lowers its outlook for the full year due to higher-than-expected medical costs, sparking a more than 20% selloff in shares that reverberated across the sector.

UnitedHealth Group Chairman Stephen Hemsley is returning to helm the health care conglomerate once again. He will replace Andrew Witty effective immediately.

Shares in UnitedHealth Group fell nearly 8 per cent in premarket trading on Tuesday after the health insurance giant suspended its annual outlook and named a new chief executive.

UnitedHealth Group (NYSE: UNH) today announced the appointment of Stephen J. Hemsley as its chief executive officer, effective immediately, following Andrew Witty’s decision to step down as CEO for personal reasons.