Dec 13 (Reuters) - UnitedHealth Group ( UNH ) CEO Andrew

Witty mourned the killing of executive Brian Thompson and said

he understood public frustrations with the "flawed" U.S.

healthcare system.

"No one would design a system like the one we have. And no

one did. It's a patchwork built over decades," Witty said in a

New York Times opinion piece on Friday, his first public

comments since Thompson, the CEO of UnitedHealth's ( UNH ) health

insurance unit, was shot dead last week.

The killing has ignited an outpouring of anger from

Americans struggling to receive and pay for medical care and has

called fresh attention to deepening resentment over health

coverage.

Witty said he and his colleagues were "struggling to

make sense of this unconscionable act and the vitriol that has

been directed at our colleagues who have been barraged by

threats."

Recent data showed that patients are now even more likely to

have their claims denied, pay more for premiums and medical

visits, and face unexpected costs for care they thought was

covered by their health plan.

"Health care is both intensely personal and very

complicated, and the reasons behind coverage decisions are not

well understood," Witty said.

"We share some of the responsibility for that. Together with

employers, governments and others who pay for care, we need to

improve how we explain what insurance covers and how decisions

are made."

Insurers say they work to negotiate down increased fees from

doctors and hospitals, as well as costly prescription drugs and

medical devices.

Following a five-day manhunt, Ivy League-educated Luigi

Mangione was charged with murder on Dec. 9 for the killing of

Thompson in a brazen shooting outside a Manhattan hotel before

an industry conference.

The New York Times reported that an internal New York City

Police report analyzing a document found on Mangione when he was

arrested concluded that he viewed the killing as a justified

response to what he believed to be corruption in the healthcare

industry.