The shooter has been apprehended and is in custody, police said.
Also on Wednesday evening the sheriff's office described the three students who were shot and wounded as seriously injured.
Spokane County Sheriff Ozzie Knezovich said one student was killed after they tried to confront the shooter after his first gun jammed. "It was several feet away from me", said Elisa, who said the shooter later walked right past her, throwing away his guns as he went.
The shooter then shot down a hallway and hit the other three students.
Knezovich called it a courageous act that prevented further bloodshed.
The student who died, according to Knezovich, attempted to dissuade the suspect from opening fire by engaging him.
Another student, Michael Harper, 15, said the suspect "was always nice and amusing and weird". He was carrying a duffel bag.
"[They] said that he was going to do something stupid where it either might get him killed or in jail", the friend told KXLY4. "He was always nice and amusing and weird".
A shooting was reported at Freeman High School in Rockford, Wash., about 20 miles south of Spokane.
Elisa Vigil, a freshman, was close enough to see the shooter, and three of the victims. KXLY-TV reports four shot, sourcing a school resource officer, while the Spokesman Review says there as many as six victims.
Schaeffer, who didn't release any information about a possible motive, said the shooting was especially hard for first responders, many of whom have children at the school. Updates to follow as more details become available. The lockdown has now been lifted, the school system tweeted. Five ambulances and a medical evacuation helicopter were called to the scene.
The deceased victim is allegedly a student at Freeman High.
Middle school students were having a late start and were just arriving at school when the shooting took place and the lockdown began, the Review reported.
Area schools have been put on preventive lockdown. "Freeman High School and the entire Spokane community will remain in my thoughts and prayers".