The brother of the 8-year-old boy who brought a loaded gun to school on Friday has been arrested, police said. The boy, whose name is being withheld because he is a minor, is 13 years old.

The kids at P.S. 91 in Brooklyn were playing outside on Friday when teachers asked them to sit on their backpacks. The 8-year-old refused to do so, and the teachers became suspicious. When they looked inside the bag, they found a loaded, seven-shot, .380-caliber pistol in a black shopping bag.

The 8-year-old was apparently having an ongoing dispute with another child, and is believed to have gotten the gun from his older brother. The 13-year-old is being charged as a juvenile with criminal possession of a weapon.

The boys' father was questioned by police and released, NY1 reports. Friday's incident was the sixth time since March that a child has been reported having a gun at a city school.

"Talk to your child," said Gregory Floyd, president of Teamsters Local 237, whose members often respond to emergencies in public schools. "If your child is having a dispute with another child, there should be something in place in the schools that they can just reconcile these issues without resulting in bringing weapons to school."

On Friday, P.S. 91 sent home notes in their children's backpacks that read, "A student was discovered carrying a weapon in his book bag. We assure you that every precaution was taken and will continue to be taken to ensure the safety of our students and staff." The Department of Education has called the incident "troubling."