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.

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.”

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 Group reported mixed financial results for Q4, with a rise in medical care ratio and CEO's tribute to the late Brian Thompson. CEO defended high healthcare costs and announced return of rebates to customers.