“I have the impression they are trying to silence everything,” Ms. Capelli said on Thursday. “Now it’s a moment of common pain, but for the future, I want justice.”

She added that, at this point, she would not know whom to sue.

Diego Federici, 35, said that his mother had the coronavirus and died on March 25 after doctors in a hospital in Treviglio, near Milan, decided not to intubate her. His father, who was never admitted to an intensive care unit, had died four days earlier.

Mr. Federici said he had joined the NOI Denunceremo Facebook group, adding that he could not accept that two healthy people had died within four days.

“Nobody is going to give me my parents back,” he said, “but if someone did something wrong, they should pay for it.”

Luca Fusco, the founder of the Facebook group, initially posted his email address for members to send their stories anonymously, but dozens of members soon started directly publishing their testimonies every day. The authors do not directly accuse health care workers of malfeasance.

As the painful stories of the epidemic pile up on Facebook, the judiciary authorities began searching for someone to blame. Prosecutors started an investigation into what they call an “involuntary epidemic” at a hospital in Alzano, near Bergamo, where the virus spread through the medical wards.

Maria Cristina Rota, Bergamo’s prosecutor, told the news agency Ansa that a pool of prosecutors would “take care of all the investigations about the epidemic in the Bergamo area.”