https://www.cnn.com/2018/02/28/us/georgia-dalton-high-school-teacher-gunfire/index.html

The incident began about 11:30 a.m. when Randal Davidson, a 53-year-old social studies teacher, refused to let students into his classroom while he was in his planning period, Frazier said. When the principal put a key in the door in an attempt to enter, Davidson fired a shot from a handgun through an exterior window of the classroom, Frazier said.