The police official was on security duty at the school because of concerns of possible militant attacks.

A police officer tasked with protecting a private school for girls in northwestern Pakistan on Tuesday opened fire at a school bus carrying teachers and students, killing an 8-year-old girl and injuring five others, officials said.

The shooting happened in the Swat Valley in Khyber Pakhtunkhwa province. Senior police official Nasir Satti said officer Alam Khan was immediately arrested. He said the shooting was not a militant attack