An armed standoff at a north central Illinois high school has ended without any injuries.

Police say an 18-year-old man carrying a shotgun entered Princeton High School Wednesday afternoon. The gunman positioned himself against a wall inside. Police say he was "highly distraught and emotional."

As officials evacuated the school, police and administrators tried to negotiate with the gunman. He eventually surrendered and was taken to an area hospital.

Princeton police say he was not a student. He's been transported to an area hospital for evaluation.

It's not yet clear why the gunman entered the school.

Police say charges are pending. An investigation is ongoing.