(CNN) -- Chaos erupted after the first student was shot. Children ran screaming and crying. Almost everyone on the playground sprinted away from the boy who had just fired a pistol at his schoolmate.
Not Michael Landsberry.
The 45-year-old math teacher calmly walked toward the gunman as he crossed the basketball court. Landsberry raised his hands to show he was no threat.
He tried to reason with the boy.
A student who witnessed the shooting said Landsberry was trying to make the shooter put his weapon down. He did not. "He took the shot right then and there," the witness said.
The entire tragedy unfolded in a mere three minutes. A popular teacher, coach and member of the Nevada Air National Guard lay dead.
His students and fellow guardsmen were stunned by his devastating death, but no one was surprised by how, directly in the face of danger, he tried to solve the crisis.
"That was the kind of person that Michael was," his brother, Reggie Landsberry, said. "He was the kind of person that if somebody needed help he would be there."
Col. Jeffrey Burkett, commander of the Nevada Air Guard's 152nd Airlift Wing, said he liked to think that Michael Landsberry -- who had been deployed once to a busy base in Afghanistan -- was using his military training when he confronted the shooter.
"He was trying to save the children. He was trying to save that child," Burkett said.
That child, the 12-year-old shooter, later turned the 9 mm pistol on himself. His identity has not been released.
Landsberry couldn't save the shooter or himself, but he did delay the gunman from going immediately after more victims.
"Mr. Landsberry's heroic actions, by stepping toward the shooter, allowed time for other students in the playground area to flee," Washoe County School District Police Chief Mike Mieras said.
As news of the shooting was reported on Twitter, students and former students tweeted about Mr. Landsberry, who taught eighth-grade math.
He can't be dead, they wrote to each other. He's strong, he'll make it, one said.
Soon the ugly realization came that he was gone.
He leaves a wife and two stepdaughters. His wife, Sharon, posted a note on Facebook, thanking her friends for their condolences.
"He was My Everything, My World!! He has touched so many lives and was an incredible Man!!," she wrote Monday night.
Landsberry, who joined the Marines after he graduated from high school in Reno in 1986, had an associate's degree in law enforcement and a bachelor's degree in education, according to a statement from the Guard. He began teaching in 2001, the same year he enlisted in the Guard, the statement said.
He worked at two other schools before moving to Sparks Middle School in 2006.
In addition to being a math teacher he also coached basketball, cross country, track and volleyball, as well as girls soccer at Sparks High School, the Guard said.
Reggie Landsberry said caring for others was something he and his brother learned from their father, who served in the Marines for 22 years. Michael Landsberry, also a veteran of the Corps, was "just a good all-around individual," his brother said.
The colonel said Landsberry "was close to a lot of people out here on the base."
A Facebook memorial page posted in Landsberry's honor had more than 16,100 likes on Tuesday afternoon.
Among the comments:
"Once a hero, always a hero! RIP."
"God bless you for the greatest act of courage and love."
"From one Air Force vet to a USMC vet, I salute you. Rest in peace, brother."
Thousands more honored the slain teacher on a "Rest Easy Mr. Landsberry" page.
On a website for his students, "Mr. Landsberry's Math Class," the slain teacher had posted pictures of himself hiking in the wilderness and standing with a weapon beside an armored vehicle.
"One of my goals is to earn your respect while you earn mine," he wrote in a message to students. "I believe that with mutual respect that the classroom environment will run smoothly."
Sparks Mayor Geno Martini called the loss of Landsberry "devastating."
"It's very unfortunate that (the life of) someone like that, who protected our country over there and came back alive ... had to be taken at his work, at a school," Martini said.
Landsberry attained the rank of corporal and served as a field wireman, Marine spokeswoman Maj. Shawn Haney said. The Guard said he was a master sergeant, who was also once deployed to Kuwait.
"A lot of lives saved by this Marine. May he guard the gates of heaven. Semper Fi, Sir," one commenter wrote on Facebook, referencing the "Always Faithful" motto of the Marines.
CNN's Larry Shaughnessy, Amanda Watts and Catherine E. Shoichet contributed to this report.