State authorities in New Hampshire are investigating a possible hate crime after a family reported that their 8-year-old boy was pushed by teenagers off a picnic table with a rope around his neck, injuring him. The boy, who is biracial, was treated in the hospital and released, the police said.

The attack occurred Aug. 28 in Claremont, a city of about 13,000 in the western part of the state, and came to light after the boy’s mother, Cassandra Merlin, posted a photograph of her son’s bloodied neck and a statement about it on her Facebook page. “It truly saddens me that even in a city so small, racism exists,” she wrote.

Ms. Merlin could not be reached for comment. She and other relatives told news outlets that their understanding of events came from the boy and his 11-year-old sister, and that there were no adults present at the time.

The boy’s grandmother, Lorrie Slattery, told Valley News, a New Hampshire newspaper, that he and others were playing in a yard in their neighborhood when the teenagers, who are white, started calling the boy racial epithets and throwing sticks and rocks at his legs.