RIVERSIDE, CALIFORNIA (BNO NEWS) -- A high school in southern California was locked down on late Wednesday morning after a suspected murder-suicide left two people killed, officials said.

The shooting happened at around 10.40 a.m. local time at the Patriot High School in Jurupa Valley, a city in Riverside County. Students at the school had just been released for lunch when several shots were heard in the parking lot.

A School Resource Officer who heard the shots immediately notified school officials and ordered a lock down. "He investigated the source of the sound and found two adults in the parking lot who were suffering from obvious gunshot wounds," said Corporal Courtney Donowho, a spokeswoman for the Riverside County Sheriff's Office.

One of those shot, an unidentified adult male, was declared deceased at the scene while an injured adult female died shortly after arriving at a local hospital. "The identities of the two decedents will be withheld pending notification of next of kin," Donowho said, adding that no students were involved.

After the shooting, officers from the Jurupa Valley Police Department and Riverside County Sheriff's Department's Special Enforcement Bureau searched every room of the school for any possible gunman. "After the incident command was satisfied that students were no longer in danger, the school lock down was lifted and parents were notified utilizing a reverse phone call system," the spokeswoman said.

Donowho said detectives from the Jurupa Valley Police Department and the Riverside County Sheriff's Department's Central Homicide Unit are investigating the shooting, but it is believed the deceased man was the shooter. "There are no outstanding suspects or persons of interest at this time but the investigation is ongoing," Donowho said.