The victims of the shooting had not yet been identified on Tuesday night.

At the time of the shooting, the owner of the market, Moishe Ferencz, had gone to a nearby synagogue, according to his mother, Victoria Ferencz.

After a couple minutes, shots rang out. The synagogue was put on lockdown, and Mr. Ferencz’s thoughts turned to his wife, Mindy, who had been left tending to the market, his mother said.

“I called my son, he says, ‘I’m locked here, I have no idea where she is,’” said Victoria Ferencz, who said she hadn’t yet heard whether her daughter-in-law was safe.

“I’m still hoping against hope,” she said.

Chesky Deutsch, a Hasidic Jew and a community activist, spoke with a shooting victim by phone. He said the victim was a man in his 20s who suffered three gunshot wounds.

Mr. Deutsch said the man did not have a clear memory of what had happened. He lives in Brooklyn and had been shopping at the store when the gunfight broke out.

Next door to the supermarket is a small synagogue and yeshiva, Mr. Deutsch said, adding that up to 100 children, ranging in age from about seven to 12, had been trapped at the yeshiva.