Two people killed in a US school shooting were a staff member and a student who was probably the attacker, police said.
Two other students were critically injured in the violence that erupted before classes began at Sparks Middle School in Nevada. Authorities said the staff member was trying to intervene.
Students from the middle school and next door elementary school were evacuated to a nearby high school, and classes were cancelled.
The first reports of the shooting came in at about 7.15am, about 15 minutes before classes were set to begin.
At the evacuation centre, parents walked with their arms around their children, some of whom were in tears.
"We came flying down here to get our kids," said Mike Fiorica, whose nephew attends the school. "It's really chaotic. You can imagine how parents are feeling. You don't know if your kid's okay."
The shooting happened on the school's campus, but outside the school building, according to police.
A spokeswoman for Renown Regional Medical Centre said says two boys were in critical condition.
Governor Brian Sandoval issued a statement after hearing about the shooting.
"I was deeply saddened to learn of the horrific shooting at Sparks Middle School this morning. My administration is receiving regular updates and the Nevada Highway Patrol is assisting at the scene," he said.
Mr Sandoval extended his thoughts and prayers to those affected.
Sparks, a city of roughly 90,000 that sprung out of the railway industry, lies just east of Reno. The school, in a working class neighbourhood, enrols about 700 students in 7th and 8th grades.
The violence erupted nearly a year after a gunman opened fire at Sandy Hook Elementary School in Newtown, Connecticut, leaving 26 dead.
Washoe County School District, which is responsible for the Sparks school, held a session in the spring in light of the Connecticut tragedy to educate parents on what safety measures the district takes.
Police said the staff member who died was was trying to protect other children from the shooter.
Between 150 and 200 officers responded to the shooting but no shots were fired by law enforcement, a spokesman said.
Of the two injured students, one is out of surgery and the other is doing well, according to police.