FOREST CITY, Iowa (AP) — Police in north-central Iowa say no children where hurt when a window of their moving school bus was shot out. The Mason City Globe Gazette reports that the incident happened in Forest City on Friday morning, when the window shattered after being hit by a shot from a pellet gun.

A statement from the Forest City School District said all children were safe and that no injuries resulted from the shooting or flying glass. Police say they know who is responsible for the shooting and believe it was an isolated incident.

Police did not name who they think is responsible and did not announce any arrests, but said a criminal investigation into the incident is ongoing.