Officers responded around 11 p.m. Saturday to the crash that ended in the parking lot of Alta Murrieta Elementary School, according to the Murrieta Police Department.
When they arrived, they found a car engulfed in flames and a man outside the vehicle with severe injuries.
Once the fire was extinguished, three occupants, including the driver, were found dead inside the car.
A family members say the man who was found alive had been pulled out of the car by a good Samaritan. The family says they're looking for that person to thank them.
A vigil for the victims was held Sunday night outside the elementary school. The individuals who died have not been identified.
Loved ones hold vigil for victims of fiery crash in Murrieta
Authorities are investigating the crash to determine a cause, but they don't believe another car was involved.