What happened to the first Caleb? What did the community do to remember him?

From the text:

The couple had lost their first Caleb, a cheerful little Four. Loss of a child was very, very rare. The community was extraordinarily safe, each citizen watchful and protective of all children. But somehow the first little Caleb had wandered away unnoticed, and had fallen into the river. The entire community had performed the Ceremony of Loss together, murmuring the name Caleb throughout an entire day, less and less frequently, softer in volume, as the long and somber day went on, so that the little Four seemed to fade away gradually from everyone's consciousness.

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