SANTA ANA, Calif. (AP) — Witnesses watched in horror as a small plane banked low in sunny skies over a Southern California shopping center and then suddenly nosedived, crashing into a parking lot and killing all five people on board.

Ella Pham and her boyfriend were walking across the lot Sunday when they saw the twin-engine Cessna plummet.

"We looked up to see the plane falling nose first," Pham, 20, told the Los Angeles Times . "It was so heartbreaking just seeing the plane crumbled into pieces."

The pilot of the Cessna 414 and all four passengers were killed, but nobody on the ground was hurt, authorities said.

Three of the victims were co-workers at Pacific Union International, a San Francisco Bay Area real estate firm, and the two others were their family members, the company said.

Nasim Ghanadan, 29, Floria Hakimi, 62, and Lara Shepherd, 42, were real estate agents based out of an office in Danville, California. Hakimi's son Navid Hakimi, 32, and Shepherd's husband, Scott Shepherd, the plane's 53-year-old pilot, were also killed.

"Our entire Pacific Union family is mourning the loss of our colleagues, family and friends," CEO Mark A. McLaughlin said in a statement. "Life is precious and we are focused on comforting the loved ones affected by this devastating event."

The plane took off from Buchanan Field Airport in Concord, California, according to Federal Aviation Administration records.

The pilot declared an emergency but didn't state the nature of his problem before crashing about a mile (1.6 kilometers) from John Wayne Airport, National Transportation Safety Board investigator Albert Nixon said Monday. Nixon didn't know how much time elapsed between the distress call and the crash.

The plane was heading to the airport southeast of Los Angeles when it came down in the lot of a Staples store and a CVS pharmacy, Orange County Fire Authority Captain Steve Concialdi said. There was no fire, he said.

Four unoccupied parked cars were struck in the crash, with one suffering major damage, Fire Capt. Tony Bommarito said.

Jesse Perez was eating lunch with a friend at Buffalo Wild Wings, which shares the parking lot, when he heard the crash.

"It sounded like a truck hit the building," he told the Orange County Register .

Customers ran from the restaurant into the lot and saw the wreckage of the white Cessna with green and blue trim.

"Bodies were hanging from out the side of the plane," said Perez, adding that emergency workers were there within minutes. "I couldn't believe what was happening."

Photos from the scene showed the plane crumpled and broken apart and the car damaged. Several roads were closed surrounding the shopping center and the busy South Coast Plaza mall across the street.

The plane is registered to a San Francisco-based real estate consulting company, Category III, according to an FAA database. A phone call to the company was not immediately returned.

"Category III is an aeronautical term which refers to a combination of highly trained pilots and sophisticated cockpit avionics working together to safely land an aircraft in zero visibility conditions," says a statement on the company's website. "We value this metaphor and work to bring Category lll precision approach to our clients to deliver better results for all aspects of complex real estate value extrications."

The 1973 Cessna was certified with the FAA through October 2019, online records show.

The Federal Aviation Administration and the NTSB are investigating the cause of the crash.

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Weber reported from Los Angeles. Associated Press writer Ariel Tu contributed from Los Angeles.