The fatal shooting last week of an executive on the streets of New York City plunged his family members and colleagues into grief. For rank-and-file employees across the health insurance industry, the killing has left them with an additional emotion: fear, with many frightened for their own safety and feeling under attack for their work.

Health insurance companies have increased security measures since the killing of Brian Thompson, the chief executive of UnitedHealthcare, and as an outpouring of online rage toward the industry has followed. Health care leaders have spoken with frustration about feeling vilified, and in the Minneapolis suburbs where United is headquartered, police officers stepped up protection of the company’s offices.

“Clearly the employees have been shaken,” said Mayor Brad Wiersum of Minnetonka, who said the city was working “just to provide that reassurance and that security, to let people know that we are going to do everything we can to keep them safe.”

One UnitedHealthcare worker who processes claims described being cleareyed about the American health care system’s shortcomings, but also believes that she and her colleagues did their best to help patients within the limits of that system. Like most workers interviewed, she did not want to be named because, given the reaction after Mr. Thompson’s killing, she feared for her own safety.

The reaction by some others to the killing, the employee said, had been startling and horrifying. The worker, who has been at the company for many years, described being told in recent days by an acquaintance that as an employee of UnitedHealthcare she was responsible for millions of people being denied lifesaving care, and that if she had any ethics, she would see the killing as the impetus to quit her job.

“Lots of us were feeling like we were horrible because we’re being accused of working for the evil empire,” the employee said. “But we all do the best we can to do a good job in the system we are in.”

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