The shots rang out, one after the other, outside San Francisco’s June Jordan School for Equity on Tuesday afternoon. At first, students shrugged off as a prank; that was, at least, until school officials triggered an immediate lockdown.

In the end, four students were shot in the parking lot of the small public high school, San Francisco Police Officer Carlos Manfredi told CNN.

According to CNN affiliate KRON, investigators are now searching for multiple suspects who may have targeted a female student who is now in critical condition.

‘Isolated incident’

The San Francisco Unified School District said the shooting was “an isolated incident outside of the school building where one student was being targeted by outsiders.”

Once the shooter struck the students, they ran across the lot toward the locked-down school for safety, CNN affiliate KGO said.

Police cleared each room in the school. About an hour later, the lockdown was lifted.

Headed to the hospital

Emergency responders later transported one victim, a 15-year-old female in critical condition, to San Francisco General Hospital to receive treatment for an upper-body gunshot wound, according to KRON.

The two of other victims, both male, received treatment at the hospital. The last student, a male teenager who walked into a police station with non-life-threatening injuries, also went to the hospital.

According to police, four male suspects, all wearing dark hoodies and jeans, remain at large. It’s unclear whether they fled on foot or in a getaway car.

School district officials tweeted that June Jordan will be open for class Wednesday. They plan to have additional “support” on hand for both the students and staff.