It was not immediately clear if the slain victim was a student at Freeman High School in Rockford, Washington, Spokane Fire Chief Brian Schaeffer told reporters at a news conference.
Schaeffer said he did not know if the suspect was a student at the school or what may have motivated the gun violence. None of the wounded victims were identified.
The fire chief described a chaotic scene at the school, with the sounds of bullets echoing through the halls prompting fears that there was more than one shooter.
Local television stations showed the school surrounded by police and fire vehicles, parents running the scene. Some parents got out of their cars and walked up to a mile rather than wait in traffic, KHQ-TV reported.
The high school has 327 students, according to U.S. News.
Three victims were in stable condition at Providence Sacred Heart Medical Center and Children’s Hospital in Spokane, said spokeswoman Nicole Stewart.
A Twitter user named Christina identified herself as a junior at the high school and said she had been evacuated following at least four shots.Read more at Reuters