As investigators continue to probe the mysterious crash of a private plane in the mountains of Virginia after it flew through restricted airspace in Washington, D.C., new details have been revealed about the four victims who died aboard the aircraft.

Adina Azarian, 49, was a well-known luxury real estate broker in New York. She and her 2-year-old daughter, Aria, were killed in the crash, said her adoptive father, John Rumpel.

"I could not love a human being more than I loved her and my grandbaby," Rumpel told The Associated Press.

Rumpel and his wife Barbara adopted Azarian, who had grown up in Connecticut and New Hampshire with her biological mother, when she was 40 years old after meeting her by chance.

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Barbara Rumpel, her daughter and granddaughter

Barbara Rumpel, left, wrote on Facebook that her daughter and granddaughter were "gone" following an outpouring of condolences after a Cessna plane crashed in Virginia with four people on board. (Barbara Rumpel / Facebook)

The couple said Azarian reminded them of their daughter, Victoria, who had died at age 19 in a scuba diving accident in 1994. The couple named the assisted living home Victoria’s Landing in Melbourne after their late daughter.

Adina Azarian

Adina Azarian and her 2-year-old daughter Aria were two of the four people killed in a plane that crashed in a remote part of Virginia on Sunday, according to Azarian's adoptive father, John Rumpel. (Lakhinder Vohra via AP)

Seven years after her adoption, Azarian conceived Aria through in-vitro fertilization.

Azarian’s nanny, 56-year-old Evadnie Smith, was also killed in the crash. Known to the family as "Nanny V," Smith lived in Azarian’s East Hampton home and traveled frequently with the mother and daughter. Smith leaves behind one son in Jamaica.

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Rumpel, himself a pilot who owns several planes, identified the pilot as Jeff Hefner, a "top shelf" aviator with decades of experience.

Jeff Hefner

Jeff Hefner was the pilot of the business jet that flew over Washington, D.C., and crashed in Virginia Sunday. He appeared to be slumped over and unresponsive, according to U.S. fighter jet pilots, officials said. (AP photo)

"I wouldn’t have had my daughter and my grandbaby fly with him if he wasn’t," Rumpel told the AP.

Hefner began his more than 40-year career in aviation as a crop duster before joining Southwest Airlines. He retired and began flying private aircraft. 

Hefner is survived by his wife and three children, said Dan Newlin, an attorney who heads a Florida law firm where Hefner worked as a flight captain.

The Cessna Citation aircraft lost contact with air traffic control shortly after taking off in Tennessee and flew to its destination on Long Island before inexplicably turning around and flying directly over the nation’s capital, prompting U.S. military fighter jets set off a sonic boom while scrambling to intercept the aircraft midair.

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The F-16 pilots reported seeing the pilot slumped over the controls in the cockpit and that the aircraft and no one on board would respond to their calls, officials said.

While the cause of the crash remains under investigation, experts theorize that the plane could have lost pressurization in the cabin, causing those inside to pass out.

The Associated Press contributed to this report.