OAK CREEK, Wis. — Amanat Singh was dancing in front of the Sikh temple here on Sunday morning, cracking up her 11-year-old brother, Abhay.

Amanat had just turned 9, and her family was responsible for preparing a birthday lunch for 300 people. The children’s parents had told the pair to stay inside the temple while they went to a store to get more paper plates.