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Editor's Note: On Tuesday, Feb. 5, 2019, after this article was published, the Orange County Sheriff's Office announced the pilot of the plane had never worked for the Chicago Police Department. For updated information, please see this article.

The pilot whose twin-engine plane crashed into a Southern California home on Sunday, killing him and four other people, was a retired Chicago Police Department officer, authorities said Monday.

Orange County Sheriff's Lt. Cory Martino identified the pilot as Antonio Pastini, 75, of Gardnerville, Nevada.

Martino told reporters that the four others who died —two were male, two were female — had not yet been identified. They were inside a single-family home in a residential section of Yorba Linda, a suburban community southeast of Los Angeles, at 1:45 p.m. when residents reported the crash.

It wasn’t clear if the people lived in the home or were guests, Martino said. He added that investigators were using DNA to identify them because of their “condition,” though he did not provide additional details.

Maja Smith, an investigator with the National Transportation Safety Board, said it wasn’t clear why the small Cessna airplane climbed to 7,800 feet then plummeted to the ground. The crash occurred just 10 minutes after takeoff from the nearby city of Fullerton, and Pastini was the only person in the plane at the time.

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Smith said that witnesses reported seeing an “in-flight breakup.”

“They saw it climbing out of a cloud at a high speed before the tail and wings started to break apart,” she said.

Damage and debris outside a home after a small plane crash in Yorba Linda, California, on Feb. 4, 2019. Five people died and two were injured after the plane came apart over the neighborhood. Amy Taxin / AP

In interviews with NBC News on Sunday, witnesses driving on the 91 Freeway said they saw what appeared to be an explosion in the sky and a trail of dark smoke. Residents in the neighborhood where the plane’s wreckage landed believed an earthquake had struck or a sports car had slammed into a home.

Smith said that wreckage was spread across four blocks and 15 or 16 homes in a “huge” debris field.

“It’s a challenge to recover all those parts,” she said.

The wreckage will eventually be gathered and moved to Arizona, where investigators will then examine the plane’s frame and engine, as well as Pastini’s pilot history and experience, Smith said.

Pastini’s daughter, Julia Ackley, described her father as an experienced pilot who had flown for decades and could operate helicopters as well as small and multi-engine planes, NBC Los Angeles reported. He often flew to Orange County to visit her and her daughter.

Ackley told NBC Los Angeles that the former police officer also owned a sushi restaurant in Nevada and a tree farm in Oregon.

She recalled her last conversation with him, and said Pastini planned to take a granddaughter flying and to see her first softball game.

“I just love him more than anything,” Ackley said.

In November, Pastini also began flying for Angel Flight West, a volunteer organization that arranges flights to and from health care facilities for people who otherwise wouldn’t be able to make the trip.

Josh Olson, the group’s executive director, said that Pastini operated one flight on Jan. 9, flying a patient with a life-threatening disease for treatment to the University of California-Davis.