A CNN report quoted Brewster County Sheriff Ronny Dodson saying that the shooting happened outside a restroom in the school's band hall.
As the victim ran outside after sustaining gunshot wound, the suspect shot herself using semi-automatic pistol. Police recovered plenty of ammunition next to the shooter's body.
An agent who was responding to the incident was inadvertently wounded through a friendly fire when another agent accidentally fired his gun.
Reports indicated that the shooter had only lived in Alpine for six months. The sheriff said he knew her grandparents, who said she was a straight "A" student and saw now indication of a potential threat.
The school, which has about 280 students, initially was placed on lockdown but authorities evacuated the students later.
Information about the motive in the shooting and the names of those involved were not yet released.
