A 15-year-old student is in custody after the assistant principal at his school in the US state of Tennessee was shot dead.
Two other administrators were seriously wounded when the student allegedly opened fire with a .22-calibre gun.
"I don't know what he was thinking or what his motives were," Sheriff Ron McClellan said.
The 1,400-student school in the town of Jacksboro was evacuated. It will remain closed for the rest of the week.
The suspect is alleged to have hidden the gun under a napkin in one of the school's common areas, before opening fire at 1400 local time (1900 GMT).
No students were injured, and the teenager was disarmed by a teacher.
"The situation could have gotten much worse. It did not because our staff followed the [emergency] plan in place," a county education board official said.
Campbell County Sheriff's office said charges were imminent, although it is not clear whether the teenager will be treated as an adult or a juvenile.
Earlier this year, a 15-year-old student in Minnesota shot dead seven people and himself at his school.