NASHUA, N.H. — Worshipers at a mosque where a rock was thrown through a window on the 15th anniversary of the Sept. 11 terror attacks believe they saw three kids walking from the building afterward, police said Monday. Twenty minutes before the rock was thrown at the Islamic Society of Greater Nashua on Sunday night, police received a report of three kids throwing rocks at a city park sign nearby. Police are investigating who threw the rock or rocks.

The Massachusetts chapter of the Council on American-Islamic Relations called on state and federal law enforcement authorities to investigate the rock-throwing as a possible hate crime. It happened on the 15th anniversary of the Sept. 11 attacks and on one of the biggest holidays on the Muslim calendar, Eid al-Adha.

“Whenever any house of worship is attacked in this manner, law enforcement authorities should investigate a possible bias motive for the crime,” CAIR-Massachusetts Executive Director Dr. John Robbins said in a statement.

The New Hampshire mosque is located in a former mill building. The society started the mosque there in April and has held open houses since then.

Muhamad Akbar said he believes three rocks were thrown at the mosque and that one nearly hit a worshiper.

“It just went past his ear,” he said. “He got shaken.”