FALMOUTH, Maine — Richard Rockefeller of Falmouth, son of banker and philanthropist David Rockefeller, died Friday morning when the small plane he was piloting crashed in Westchester County, New York.

Rockefeller, an experienced pilot, flew to New York on Thursday to celebrate his father’s 99th birthday, family spokesman Fraser Seitel told the Bangor Daily News.

His Piper Meridian single-engine turbo prop crashed just after 8 a.m. near the Westchester County Airport. Rockefeller, 65, was the only person aboard the plane when it crashed.

“This is a terrible tragedy, and the family is in shock,” Seitel said. “Richard was a wonderful and cherished son and brother, husband, father and grandfather. It’s just horribly sad.”

Rockefeller was father to two adult children and had several grandchildren, Seitel said. He was one of David and Peggy Rockefeller’s six children.

Rockefeller practiced and taught medicine in Portland from 1982 to 2000, according to the Rockefeller Brothers Fund website.

During the 1980s, he practiced at Bayview Pediatrics in Yarmouth with a group of physicians including Dr. Donald Abbott.

On Friday, Abbott remembered Rockefeller as “down-to-earth, caring … just a regular guy.”

“He had very high principles about how he wanted to lead his life,” Abbott said. “He went into family medicine because he really believed in it and thought it was a great way to help people. He did a great job at it and patients really liked him.”

Rockefeller was active in Doctors Without Borders, founded an institute to improve medicine using computer-based technology, and most recently had worked with veterans diagnosed with post-traumatic stress disorder.

“He thought it was tragic what’s happening with veterans who came back from Iraq and Afghanistan, and he set about some years ago to try to find a treatment,” Seitel said. “He was making great progress.”

Former Maine Gov. John Baldacci met with Rockefeller several years ago at Bangor International Airport to discuss the physician’s research into PTSD.

“He would go anywhere to see anyone in regards to this very important issue,” Baldacci said by phone. “What struck me about him was that he had found something that would be very helpful and he wanted to bring that to everybody’s attention. He was doing it at his own expense because he really cared deeply for the military — active duty and retired and the veteran community.”

Rockefeller also chaired the board of Maine Coast Heritage Trust from 2000 until 2006.

Maine’s congressional delegation offered condolences to Rockefeller’s family, and noted his dedication to improving health care in the country and around the world.

“Maine is better off because of Richard’s commitment to making it a better place to live,” Rep. Mike Michaud, D-2nd District, said in a statement.

Richard Rockefeller’s plane was scheduled to take off from Westchester County Airport at 8:13 a.m. Friday and arrive in Portland at 9:27 a.m.

At 8:15 a.m., Harrison police received a report that a plane had crashed in the backyard of a home and horse stable in Purchase, New York, about a half-mile from the runway, Harrison Police Chief Anthony Marraccini said. The plane landed about 20 feet from the home, but no one on the property was injured.

Officials from the Federal Aviation Administration and National Transportation Safety Board are investigating the crash.