Twenty to thirty students were witnesses to the tragedy that also left the lone suspected gunman dead, police said. It's unclear whether the student committed suicide, but authorities say no shots were fired by law enforcement. Police said between 150 and 200 officers, including some from as far as 60 miles away, responded to the shooting.
"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.
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.
Senate Majority Leader Harry Reid, D-Nevada, offered his condolences to those 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," Reid said in a statement.
The school, located in a working class neighborhood, enrolls about 700 students in 7th and 8th grades.
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.
In a statement on the website of Sandy Hook Promise, a gun control advocacy group, Nicole Hockley, whose son Dylan was killed in the shooting said, "It's moments like this that demand that we unite as parents to find common sense solutions that keep our children--all children--safe, and prevent these tragedies from happening again and again."
Washoe County School District held a session in the spring in light of the Connecticut tragedy to educate parents on what safety measures the district takes.
Sparks, a city of roughly 90,000 that sprung out of the railway industry, lies just east of Reno.
Mayor Geno Martini spoke at a morning press conference to assure residents that the community was safe.
"It's a tragic day in the city of Sparks," he said. "This is just an isolated incident."