With the arrival of cold weather in the fall, he knew the growing migrant population in Bayonne could no longer stay in one of the city’s main squares, where people had been camping out.

“It was cold and raining,’’ Mr. Etchegaray said. ‘‘We couldn’t leave them there anymore. They were cold, sick and hungry.”

The mayor formed plans for the initiative quickly. “He came directly to the square,” Ms. Etcheverry recalled, adding that she remembered him saying, “I’ll be back in a half-hour.”

When he returned, he led volunteers and migrants to an underground parking lot for the municipal police — a temporary solution until something better could be found.

“He accompanied them, and showed them where the toilets were,’’ Ms. Etcheverry recounted. “He saw that they were quiet, and that we were just young people helping other young people. But we never imagined that it would end like this, in a center financed by the municipality.”

It is a mayor’s duty, Mr. Etchegaray said.

“The state just doesn’t want to know,” he added. “But me, I’ve got to know. And this was an emergency.”