Authorities had earlier said that the deputy had accidentally shot herself in the leg.
Sheriff's officials released updated information in the afternoon, stating that another deputy unintentionally discharged his firearm, striking his partner.
The two were sitting in their patrol vehicle at the time, preparing to start their shifts shortly after 5 a.m. at the South L.A. station.
The injured deputy -- who has not been identified -- was transported to Harbor-UCLA Medical Center in Torrance, where she was treated and listed in stable condition.