WASHINGTON TOWNSHIP, N.J. — The authorities in southern New Jersey said Saturday that they had arrested a 16-year-old boy for activating a public-address system at a Wal-Mart store last week and ordering “all black people” to leave.

The boy, from Atlantic County, was charged by Gloucester County authorities with bias and intimidation and harassment in connection with the episode last Sunday. If convicted, he could face up to a year in a juvenile detention center, officials said. His name was not released because he is a minor.

According to the police, the boy picked up a public-address telephone in the Wal-Mart in Washington Township, one of two dozen accessible to the store’s customers, and said, “All black people, leave the store now.”

A store manager quickly apologized over the public-address system, witnesses said, and the police and the store opened separate investigations that included a review of images captured by the store’s security cameras.