3 Students Shot Outside San Francisco High School: Police

— -- Three students were shot outside a San Francisco public high school Tuesday afternoon, police said.

One female victim was in critical condition, while two male victims suffered minor injuries, according to the San Francisco Police Department. The female victim may have been targeted they said, adding that the incident was "not a random shooting."

Nearly three hours after San Francisco Police first announced the incident, it tweeted, "A 4th victim walked into #SanFranciscoGeneral Hospital with non-life threatening injuries related to this incident." No further information about the nature or cause of the injury was provided.

The victims ran into the school after they were shot, police said, and four male suspects in dark jeans and hoodies were seen running away. Police weren't aware whether the suspects were students, and no one has been taken into custody.

June Jordan High School for Equity was placed under lockdown following the shooting, and the victims were transported to local hospitals, according to the San Francisco Fire Department.

ABC News' Jonah Lustig contributed to this report.

This is a breaking news story. Please check back for updates.