NASHVILLE, United States (AP) – The person who killed three children and three adults at a Christian school in Nashville legally bought seven firearms in recent years and the shooter hid the guns from parents before the attack, police said Tuesday.

The violence Monday at The Covenant School is the latest school shooting to roil the nation. Three nine-year-old students were killed, as well as the head of the grade school, a custodian, and a substitute teacher.

The suspect, Audrey Hale, 28, was a former student at the school. Police said the shooter did not target specific victims.

Authorities said Hale was not on their radar before the attack but said the shooter was under a doctor’s care for an undisclosed emotional disorder.

Police earlier said Hale had drawn a detailed map of the school, including potential entry points, and conducted surveillance of the building before carrying out the massacre, authorities said.

Surveillance video of The Covenant School grounds, released by police, showed a time stamp of just before 10:11 am when the glass doors were shot out by the shooter. Police said they received a call about a shooter at 10:13 am but had not said precisely what time they arrived, and the edited bodycam footage didn’t include time stamps. A police spokesperson didn’t immediately respond to an email Tuesday asking when they arrived or whether any version of the video includes time stamps.

Police have given unclear information on Hale’s gender. For hours Monday, police identified the shooter as a woman. At a late afternoon press conference the police chief said Hale was transgender. After the news conference, police spokesperson Don Aaron declined to elaborate on how Hale identified.

In an email Tuesday, police spokesperson Kristin Mumford said Hale “was assigned female at birth. She used male pronouns on a social media profile. The victims were: Evelyn Dieckhaus, Hallie Scruggs and William Kinney, all age 9. The adults were Cynthia Peak, 61; Katherine Koonce, 60; and Mike Hill, 61.