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, just weeks after the shooting of Brian Thompson brought attention to the industry.

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.”

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

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.