Before he received his second shot of a Covid-19 vaccine, there was little reason to think that George Watts Jr. was about to die.

He was 24 and showed no obvious heath problems. His family said he lived cautiously. He spent most of his time playing video games in his room at his parents’ house in Elmira, a city in south-central New York.

That is where he was when he collapsed on Oct. 27, 2021.

George Jr.’s mother, Kathy, called 911 and started C.P.R. Paramedics rushed him to the emergency room, where doctors pronounced him dead.

What happened?

To the family, the answer was instantly obvious. “I blame that damn Covid vaccine,” Ms. Watts said in the hospital’s waiting room after learning her son had died, according to her husband, George Watts Sr.