UnitedHealth posted a better-than-expected fourth-quarter profit, but a nagging rise in medical costs and care utilization surprised Wall Street.

In its first results since its insurance unit CEO was fatally shot in New York City, UnitedHealth Group reported Thursday weaker-than-expected fourth-quarter revenue, prompting its shares to fall in early morning trading despite quarterly profit beating projections.

UnitedHealth CEO Andrew Witty said on Thursday that healthcare in the U.S. needs to be "less confusing, less complex and less costly" during the company's first earnings call since the murder of Brian Thompson,

The UnitedHealth Group leader whose murder in December unleashed a torrent of public frustration and dissatisfaction with the U.S. health care system was pushing for some of the very improvements that critics have been seeking.