SPARKS, Nev. >> Students at a Nevada middle school were filing off buses and reuniting with friends on the playground after a week-long vacation when the pop of gunfire shattered the morning calm. Children fled the campus for their lives before the first bell rang.

Police said a Sparks Middle School student was the lone shooter who injured two classmates, killed himself and took the life of an 8th-grade math teacher who tried to stop the rampage Monday. The teacher, 45-year-old former serviceman Michael Landsberry, was being hailed for trying to protect students from a shooting that was witnessed by 20 or 30 children.

"We have a lot of heroes today, including our children … and our fallen hero, an amazing teacher," Washoe County School District Superintendent Pedro Martinez said.

Authorities did not provide a motive for the shooting, and it’s not known where he got the gun. The 12-year-old wounded students were listed in stable condition. One was shot in the shoulder, and the other was hit in the abdomen.

Jose Cazares said he was hanging out with friends when they heard gunshots, which they thought were firecrackers. He said he saw a boy shoot two students. He said the boy then aimed the gun at his chest, but Landsberry stepped between him and the shooter.

"He was telling him to stop and put the gun down. Then the kid, he yelled out ‘No!’ Like, he was yelling at him, and he shot him," Jose told NBC’s "Today" show today. "He was calm, he was holding out his hand like, ‘put the gun in my hand.’"

Jose said he and his friends ran and hid after Landsberry was shot. He said one friend began crying, which the shooter heard. The shooter found the boys and threatened to shoot them if they told anyone they saw him, then fired two shots at a window, before apparently running out of bullets, Jose said. He said the boys lied to the shooter, telling him they didn’t see anything, and then the shooter ran off.

Jose’s mother expressed gratitude for Landsberry, who she said had never taught her son.

"He sacrificed his life to take our kids into safety," Marisela Cazares told "Today." ”I thank him for that. He’s a true hero."

After the gunfire stopped, parents clung to their teary-eyed children at an evacuation center, while the community struggled to make sense of the latest episode of schoolyard violence to rock the nation less than a year after the massacre in Newtown, Conn. Sparks, a city of roughly 90,000 that sprung out of the railway industry, lies just east of Reno.

"It’s not supposed to happen here," said Chanda Landsberry, the slain teacher’s sister-in-law. "We’re just Sparks — little Sparks, Nevada. It’s unreal."

Investigators were still trying to piece together the chain of events that began around 7:15 a.m. Monday, 15 minutes before classes were set to begin for roughly 700 students in the 7th and 8th grades.

"As you can imagine, the best description is chaos," Reno Deputy Police Chief Tom Robinson said. "It’s too early to say whether he was targeting people or going on an indiscriminate shooting spree."

It was no shock to family members that Landsberry — a married military veteran with two stepdaughters — would take a bullet.

"To hear that he was trying to stop that is not surprising by any means," Chanda Landsberry said. 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 Mayor Geno Martini said Landsberry served two tours in Afghanistan with the Nevada National Guard and was well known in the school community.

"He proudly served his country and was proudly defending the students at his school," he said. The mayor praised the quick response from officers who arrived at the scene within 3 minutes of the initial 911 calls to find the shooter with a self-inflicted gunshot wound to the head.

"They got it under control very quickly and shut down the scene," said Martini, who urged listeners on a local radio station hours after the shooting to be sure all guns in their homes are locked away safely.

"I couldn’t understand how this kid got a gun," he said. "I’m sure his parents didn’t give it to him."

Students from the middle school and neighboring elementary school were evacuated to the nearby high school, and classes were canceled. The middle school will remain closed for the week along with an adjacent elementary school.

"We came flying down here to get our kids," said Mike Fiorica, who came to the evacuation center to meet up with his nephew, a Sparks Middle school student. "You can imagine how parents are feeling. You don’t know if your kid’s OK."

The violence erupted nearly a year after a gunman horrified the nation by opening fire in Sandy Hook Elementary School in Newtown, Conn., leaving 26 dead. The Dec. 14 shooting ignited debate over how best to protect the nation’s schools and whether armed teachers should be part of that equation.

The Washoe County School District, which oversees Sparks Middle School, held a session in the spring in light of the Connecticut tragedy to educate parents on what safety measures the district takes.

The district has its own 38-officer police department. No officers were on campus at the time of the shooting.

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Associated Press writer Michelle Rindels in Las Vegas and news researcher Rhonda Shafner in New York City contributed to this report.