UnitedHealth reported fourth-quarter results on Thursday that reflected persistent challenges for the health insurance sector.

In his first public comments since one of his executives was shot to death, UnitedHealth Group CEO Andrew Witty said the healthcare system “needs to function better.”

The CEO of UnitedHealth Group has defended its role in America's health system as the company posted its first earnings results since the murder of one of its top executives. Sir Andrew Witty spoke to analysts as the firm reported mixed results,

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.

UnitedHealth shares dropped nearly 5% Thursday morning after the firm disclosed worse-than-expected revenue in its first earnings report since the shocking assassination of Brian Thompson, its insurance branch’s chief executive.