"In my estimation, he is a hero. ... We do know he was trying to intervene," Reno Deputy Police Chief Tom Robinson said about the fallen staff member.
Landsberry was a military veteran who leaves behind a wife and two stepdaughters, said his sister-in-law Chanda Landsberry. She said she wasn't surprised he stepped in to stop the rampage.
The motive isn't yet known. Names of the suspect and victims haven't yet been released.
"As you can imagine, the best description is chaos," Robinson said. "It's too early to say whether he was targeting people or going on an indiscriminate shooting spree."
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.
At the evacuation center, parents comforted their children.
"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."
One of the students injured in the violence that erupted around 7:15 a.m. is out of surgery and the other is doing well, according to police.
The shooting happened on the school's campus and ended outside the school building itself, according to police.
"I was deeply saddened to learn of the horrific shooting at Sparks Middle School this morning," Nevada Gov. Brian Sandoval said in a statement extending his thoughts and prayers to those affected.
About 700 students in 7th and 8th grades are enrolled at the school, located in a working class neighborhood.