In the wake of the shooting, a number of politicians and industry officials expressed shock and sympathy.
Michael Tuffin, president of insurance industry organistion Ahip, said he was “heartbroken and horrified by the loss of my friend Brian Thompson”.
“He was a devoted father, a good friend to many and a refreshingly candid colleague and leader.”
In a statement, UnitedHealth Group said it had received many messages of support from “patients, consumers, health care professionals, associations, government officials and other caring people”.
But online many people, including UnitedHealthcare customers and users of other insurance services, reacted differently.
Those reactions ranged from acerbic jokes (one common quip was “thoughts and prior authorisations”, a play on the phrase “thoughts and prayers”) to commentary on the number of insurance claims rejected by UnitedHealthcare and other firms.
At the extreme end, critics of the industry pointedly said they had no pity for Thompson. Some even celebrated his death.
The online anger seemed to bridge the political divide.
Animosity was expressed from avowed socialists to right-wing activists suspicious of the so-called “deep state” and corporate power. It also came from ordinary people sharing stories about insurance firms denying their claims for medical treatments.
Mr Montes-Irueste of People’s Action said he was shocked by the news of the killing.
He said his group campaigned in a “nonviolent, democratic” way – but he added he understood the bitterness online.
“We have a balkanised and broken healthcare system, which is why there are very strong feelings being expressed right now by folks who are experiencing that broken system in various different ways,” he said.