When the war forced Nasser al-Zaanin to flee his home in northern Gaza in October, he, along with his adult sons and grandchildren, moved to a school that had been turned into a shelter.

There, at the Abdul Kareem al-Aklouk school in the town of Deir al Balah, he helped set up a system of committees to improve life for families who had taken refuge. The committees oversaw food, water and medical needs, and they had one red line: No armed men were allowed in the compound.

Residents, already forced to evacuate their homes because of Israel’s intense bombardment, wanted to avoid becoming a target for Israeli forces hunting down Hamas militants. Every few days in recent weeks, Israel has hit a school building turned shelter where it has said militants are hiding, including on Saturday, when it struck two compounds in northern Gaza that it said Hamas was using as a military base.

Early in the conflict, Mr. Zaanin said, Hamas had wanted to station police officers at the shelter where he was staying. The group said it would ensure security, but he said the residents had gathered to stop that.

“All the families agreed,” said Mr. Zaanin, 56, who once worked as a civil servant for the Palestinian Authority in Gaza.

“We simply want to save all families, women and children and not let there be any potential threat against us because of the existence of police and members of the Hamas government,” he said. The police, Mr. al-Zaanin added, could stand outside the building but not inside.