BOSTON -- Three people were killed Tuesday when the plane they were in crashed nose-first into a shopping plaza parking lot in Easton.

Angel Flight Mourns Victims | Three Killed In Plane Crash | Angel Flight's Record Eyed

Easton police identified the couple as Robert Gregory, 43, and Donna Gregory, 37, both of Riverhead, N.Y.

Easton police identified the pilot as Joe Baker, of Brookfield, Conn. FAA officials said Tuesday's flight originated in Westhampton, N.Y., and Camerlin said Baker had joined the network in November.

The Federal Aviation Administration said the plane was part of Angel Flight Northeast, a network of local pilots who volunteer to run medical flights at no charge to the patients.

Larry Camerlin, the founder and president of Angel Flight NE, said a cancer patient and his wife -- a couple in their 40s with children -- were being flown to Boston's Logan International Airport so the man could be treated at the Dana-Farber Cancer Institute.

"People were running in the parking lot like they heard the plane, and they were running before it hit." - Patty Desgrosseillies Witness

The plane crashed at about 10:20 a.m. Tuesday at the Highlands Plaza near the Hannaford grocery store. The plaza is located on Robert Drive off Route 106.

"What we can tell is there were three fatalities in the aircraft. As to what happened, as to what may have transpired prior to that, we don't know at this point," said Wally Bunker, of the Massachusetts Aeronautics Commission.

Witnesses Describe Seeing 'Big Ball Of Flames'

Easton Deputy Police Chief Allen Krajick, a pilot himself, said that he saw the plane flying very low moments before the crash and knew the aircraft was in trouble.

"I knew he was in trouble, obviously, at that altitude and attitude nose-down like that. That is not a maneuver they would ever do in an area like this, on a day like this," he said.

Witnesses said people on the ground ran for cover moments before the plane crashed into a remote corner of the paved parking lot. The plane, a single-engine Beech Bonanza, burst into flames when it hit the ground, witnesses said.

"People were running in the parking lot like they heard the plane, and they were running before it hit. I don't believe anybody on the ground was hurt," said witness Patty Desgrosseillies, the manager of the nearby Bank of Easton.

"I saw a plane just going very straight, no landing gear, and it just nose-dived. In one second it completely blew up with one big ball of flames," said witness Jean Ryan.

Some witnesses said it looked as though the pilot tried to make an emergency landing on the parking lot.

"I saw the plane going around, and I think he was trying to land ... they were going to use (the parking lot) to land," said witness Phyll Aguian.

"From when I first heard it to when I saw it, (the pilot) did maneuver, he turned. But I don't know what was going inside the cockpit at the time," Krajick said.

Officials Comb Over Wreckage, Investigate Cause

The plane did not hit any buildings or cars, and no one on the ground was injured. The cause of the crash is unknown.

Krajick said the plane's propeller was found in the woods about 50 yards from the wreckage.

Angel Flight NE is a network of 962 volunteer pilots from the New England area who fly patients and their families to hospitals to receive critical care treatments. The costs are covered by the pilots and private and corporate donors, according to its Web site.

The Angel Flight NE has flown more than 53,000 adults and children on more than 30,000 missions without any fatalities or crashes, Camerlin said.

Camerlin said Angel Flight Northeast, based at the Lawrence Municipal Airport in North Andover, Mass., is a separate entity from other Angel Flight groups, but all operate under the umbrella of Air Charity Network.

"We take very seriously our moral obligation to take the finest care and provide the highest level of safety for all our patients and passengers. This is an extremely difficult day for all of us at Angel Flight. Our prayers, concerns and focus is on the families," Camerlin said.

The plane is registered to Janet Keene, of Brookfield, Conn., but she was not the pilot or aboard at the time of the crash. Camerlin said Keene was in "absolute and total shock."

"I want to offer our heartfelt condolences to our patient's family, and to all the people affected by this tragedy. This is a horrible, unexpected loss," Dana-Farber President Dr. Edward J. Benz said in a statement. "I also want to offer my deepest sympathies to the family of the Angel Flight pilot killed today, and to the people of Angel Flight. Angel Flight volunteers give greatly of themselves and their resources. Their selfless work makes it possible for many people to get lifesaving care that might otherwise be out of reach."

Last month, an Angel Flight plane crashed shortly after takeoff near Tampa, Fla., killing all three on board, including a 49-year-old cancer patient, a 15-year-old boy and the 81-year-old pilot.

Team 5 Investigates found there have only been six fatal crashes in the entire Angel Flight network's 25 year history.