Dr. Richard Rockefeller, the great-grandson of oil tycoon John D. Rockefeller, was killed Friday morning when his small plane crashed shortly after taking off from a suburban New York airport.

Officials say that the 65-year-old Rockefeller heir was the only person on board when the Piper Meridian single-engine turboprop crashed into trees. The cause of the crash, however, was not immediately clear.

Rockefeller, the son of the billionaire and prominent philanthropist David Rockefeller, took off into dense fog and steady rain from the Westchester County Airport in Purchase, 23 miles north of New York City, at 8:08 a.m. reports the New York Times. However, less than 10 minutes into the flight, the Federal Aviation Administration notified airport officials that it could not reach the pilot. The FAA later discovered that the plane crashed into trees on a horse farm about a half mile away and broke into many pieces.

Family spokesman Fraser P. Seitel said that Rockefeller flew to New York on Thursday to celebrate his father's 99th birthday, and that he was returning home to Maine.

"There were foggy conditions outside. You can only see about a quarter mile down the runway," he said, according to Reuters. "Those are extreme conditions for the airport."

Seitel added that "Richard was an experienced pilot, who had flown for many years."

The FAA and National Transportation Safety Board are investigating the crash.

Rockefeller practiced and taught medicine in Portland, Maine. He also served on the advisory board to Doctors Without Borders and was a former chairman of the Rockefeller Family Fund. He leaves behind his wife and two grown children.