I take it that you are referring to the first chapter of this excellent dystopian novel, when a strange aircraft flies over the community that Jonas is not used to. Jonas and other citizens await an explanation and they are told to go into the nearest building, leaving their bicycles on the ground. We are told that Jonas "instantly, obediently" left his bicycle on the ground and went into his home. His parents were both and their work and his sister was at her Childcare Centre, so he was by himself. As Jonas wonders what has happened, he looks out through the windows of his house, and is shocked to see nobody else outside, only abandoned bikes. This makes him very frightened:
He had been frightened then. The sense of his own community silent, waiting, had made his stomach churn. He had trembled.
Clearly he is not used to such silence and emptiness in his community, where things like this do not happen. This is part of why he is frightened and scared.