Police on Monday identified the Nashville school shooter as 28-year old Audrey Hale, a biological woman who identified as transgender. Hale was shot and killed by police at the Covenant School after killing six people.

Hale entered the school through an open door and used a staircase to reach the second floor, police say, before shooting and killing six people, including three children. Hale previously attended the school.

Nashville police chief John Drake said Hale may have planned the attack and that a manifesto and map of the school grounds were found in the shooter’s house.

“We have also determined that there were maps drawn in detail of surveillance entry points. At one point she was a student at that school,” Drake said. “There was a vehicle nearby that gave us a clue as to who she was.”

The Covenant School where the shooting took place is a private Christian school for students from pre-school to the sixth grade.