The shooter who killed three students and three staff members at a Christian school in Nashville legally bought seven weapons in recent years and hid the guns from their parents before the attack by firing indiscriminately at victims and spraying gunfire through doors and windows, police said Tuesday.

The violence Monday at The Covenant School was the latest school shooting to roil the nation and was planned carefully. The shooter had drawn a detailed map of the school, including potential entry points, and conducted surveillance of the building before the massacre, authorities said.