"I was hiding under a desk. It was terrifying," the mother of a student at the school tells PEOPLE

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The mother of a child at Sandy Hook Elementary School shared her experience of the mass shooting with PEOPLE Friday afternoon.

When our reporter spoke with the woman – who went to the school Friday morning with a book for her child – she was crying and said, “I was hiding under a desk. It was terrifying my friend’s kids are dead.”

The woman’s children are currently safe at the local firehouse and she is waiting for police to release them. She adds that when the students were evacuated from the school, they were instructed to look away from the office of Principal Dawn Hochsprung, who was killed in the shooting, when they walked past.

A federal official tells PEOPLE that 27 people were killed in the school Friday morning, including 20 children.

According to the woman, the shooter, Adam Lanza, who was also confirmed dead at the scene “went into the office, started arguing, and he killed people in the office,” before going into a classroom.

Another parent visiting the school at the time tells PEOPLE he “could hear shots in the hall and glass breaking.” And an NPR interview with one of the school’s teachers revealed that the school’s PA system was on the whole time, amplifying the shots throughout the school.