"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.