A teacher at a middle school in Nevada was shot and killed while trying to protect children after a student arrived on campus Monday and started opening fire before turning the weapon on himself, police say.

One male student injured in the shooting at Sparks Middle School in Sparks, Nev., has gone through surgery, while the other is doing well, Washoe County School District Chief of Police Mike Mieras said during a news conference.

Family members identified the staff member who was killed as math teacher Michael Landsberry, a 45-year-old military veteran who leaves behind a wife and two stepdaughters.

The gunman died of a self-inflicted gunshot wound after turning the semi-automatic handgun on himself, authorities said.

A Sparks police dispatcher said reports of the shooting -- which happened on the school's campus, but outside the school building itself -- started coming in at 7:16 a.m. local time.

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Police said between 150 and 200 officers responded to the shooting.

Kyle Nucum, a 13-year-old student, told the Reno Gazette-Journal that he saw a classmate shoot a teacher.

“We were at the basketball court and we heard a pop, like a loud pop, and everybody was screaming and the teacher came to investigate – I thought it was a firecracker at first, but the student was pointing a gun at the teacher after the teacher told him to put it down and the student fired a shot at the teacher and the teacher fell and everybody ran away," he said. “And we ran across the field to get somewhere safe and while we were running we heard about four or five more shots and we just got somewhere safe. This lady let us into her house.”

Authorities believe Landsberry was trying to protect students when he was killed. He just celebrated his wedding anniversary on Oct. 18, The Las Vegas-Review Journal reported.

“My estimation is that he is a hero,” said Reno Police Department Deputy Chief Tom Robinson.

Police said there is no apparent motive yet for the shooting and they believe the gunman acted alone.

"To hear that he was trying to stop that is not surprising by any means," said his sister-in-law Chanda Landsberry. She added his life could be summed up by his love of family, his students and his country.

On his school website, Michael Landsberry posted a picture of a brown bear and took on a tough-love tone, telling students, "I have one classroom rule and it is very simple: `Thou Shall Not Annoy Mr. L."'

"The kids loved him," Chanda Landsberry said.

Sparks Middle School will remain closed for the rest of the week.

Washoe County School District spokesman Charles Rahn told the Associated Press that the middle school and the adjacent Agnes Risley Elementary School were evacuated to Sparks High School. Rahn said the elementary school will stay closed Monday.

At the evacuation center, 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 OK."

Nevada Gov. Brian Sandoval said in a statement that he was "deeply saddened to learn of the horrific shooting."

“My administration is receiving regular updates and the Nevada Highway Patrol is assisting at the scene," he added.

Senate Majority Leader Harry Reid, D-Nev., offered his condolences to students, parents and staff who experienced "a traumatic morning."

"No words of condolence could possibly ease the pain, but I hope it is some small comfort that Nevada mourns with them. I stand by to be of any assistance if there is anything that can be done," Reid said in a statement.

The school, which enrolls about 700 students in 7th and 8th grades, has a strict uniform policy that forbids the colors red and blue in students' outfits, colors commonly associated with rival gangs.

Sparks, a city of roughly 90,000, lies just east of Reno.

The Associated Press contributed to this report.