The Sheriff's Department says in a statement that the incident occurred in Pomona on Saturday shortly around 9:45 p.m.
The sheriff's department says officers in a multijurisdictional gang taskforce were driving through a parking lot when a female suspect confronted them with a gun.
She was shot and pronounced dead at the scene where police recovered a handgun.
Her identity has not been released.
The sheriff's department is assisting Pomona police with the investigation.