An eighth-grader opened fire with a pistol Tuesday outside his middle school cafeteria, injuring two classmates, authorities said.
"It was a heroic job done," he said. "She de-escalated a very dangerous situation."
James S. Newman, 14, was charged as an adult with attempted murder and was jailed on $150,000 bail, Donnelly said. He also was charged with use of a deadly weapon and use of a firearm by a minor.
The victims' injuries were not life-threatening, he said. A boy was treated for a gunshot wound to arm, and a girl was treated for a superficial leg wound from shrapnel.
Donnelly said the victims had no relationship with the suspected gunman, nor had they had any disputes or arguments with him.
"It appears he decided to engage in school violence," the officer said. "He brought a gun to school today and randomly targeted these two students."
Investigators were withholding the names of the victims and the teacher, who school officials said did not want to be identified.
Police recovered the .38-caliber pistol, and were trying to determine where the boy got it.
More than a dozen students and others witnessed the shootings just before 9 a.m., police said. When the teacher heard three gunshots, she came out into the hallway from a nearby room and confronted the boy, Donnelly said.
"She basically challenged him, verbally challenged him, `Drop the gun, put the gun down,"' Donnelly told KKOH radio in Reno. "She empathized with him, tried to be understanding and de-escalated the situation."
As a precaution, authorities put the school on lockdown for about an hour, then canceled classes.
"Some people were crying," Jamie Coombs, who was in math class at the time, told KOLO-TV. "They made us stay in the classroom and bolt the door and put papers up against the windows."