The plane hit a vehicle but nobody in the auto was hurt, said Stephen Concialdi, spokesman for the Orange County Fire Authority.
Plane's final moments caught on vehicle dashcam outside of John Wayne Airport in Santa Ana.
The family of one of the victims identified their daughter, 29-year-old Nasim Ghanadan of Danville, as one of those aboard the plane when it crashed.
The pilot of the Cessna 414 declared an emergency before crashing about a mile (1.6 kilometers) from John Wayne Airport, Federal Aviation Administration spokeswoman Arlene Salac said.
The plane, which took off about in Concord, about 400 miles up the coast from Sant Ana, banked low before it nose-dived into the ground, witnesses said.
Ghanadan's profile on the company website said her clients "appreciate her honesty, tenacious work ethic, strong negotiation skills, and cheerful spirit".More news: Indian central bank raises rates for second time
The plane crashed just a block away from South Coast Plaza, a large mall.
It crashed in a parking lot for Staples, a CVS pharmacy and other retailers, said Captain Tony Bommarito of the Orange County Fire Authority.
The FAA launched an investigation into the crash, and added that the National Transportation Safety Board will determine the probable cause.More news: President Kiir, all opposition leaders sign governance agreement
Category III Aviation Corp, a San Francisco real estate firm, owned the plane, FAA records showed. Customers ran out of a nearby restaurant and saw the wreckage of the white plane with green and blue trim. A phone call to the company was not immediately returned.More news: Russia to deploy military police on Occupied Golan Heights
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