The shooting occurred at about 10:40 a.m. in the parking lot outside of the school, located at 4355 Camino Real, south of the 60 Freeway.
The school was locked down shortly after a campus security guard heard shots and called for a "code red."
According to the Riverside County Sheriff's Department, no students were involved in the shooting, which reportedly involved two adults in a murder-suicide attempt.
"At this point, they're both adults, and they appear to have some sort of relationship," said Riverside County Sheriff's Sgt. Joe Borja.
Investigators say the woman is a bilingual studies volunteer. She was hospitalized, where she later died.
The man was pronounced dead at the scene.
Several students on campus witnessed the shooting. They were interviewed by sheriff's investigators.
The school sent a phone message to parents informing them of the shooting.
Parents gathered outside of the school, worried about their sons and daughters. They were assured by authorities that no students were involved in the incident and that investigators are combing the campus to ensure the safety of students and staff members.
Parents crowded around the school reported receiving text messages from their children about the lockdown situation. Students said they were told they must remain in their classrooms, but they were not briefed on the details of the shooting.
Sheriff's deputies declared the campus secure shortly before noon and cleared school officials to resume normal operations.
Three and a half hours after the lockdown, students were released to their parents.
The investigation remained ongoing Wednesday afternoon.
The names of the deceased were not released pending notification of next of kin.