Samuel Roy Quinn spent five hours with his mother on Friday, finally allowed to say goodbye as her condition deteriorated in a nursing home south of Houston. He held her hand and hugged her. He removed his face mask several times to kiss her on the forehead.

When he eventually left the nursing home, The Resort at Texas City, an employee ran after Mr. Quinn to tell him — for the first time — that his mother had tested positive for the coronavirus, he said.

It turned out that Mr. Quinn’s mother, Peggy Smith, was one of 83 residents and employees at the 135-bed facility who tested positive for the virus, according to local health officials. Some residents are still waiting for results.

Mr. Quinn said his 87-year-old mother, who had Alzheimer’s disease, died on Saturday morning.

“I would have not stayed there that long if I knew she had coronavirus,” Mr. Quinn, a fence builder, said from his home in the nearby town of San Leon, where he is now grieving in self-quarantine.