A small plane carrying a cancer patient to Boston went into a nosedive and crashed Tuesday in a grocery store parking lot, killing all three people on board, authorities said. It was the third fatal crash in as many months of a charity flight carrying a patient to medical treatment.

The single-engine Beechcraft Bonanza went down in the parking lot of a Hannaford store in Easton, about 25 miles south of Boston, about 10:15 a.m., Federal Aviation Administration spokesman Jim Peters said.

Click here for photos.

The plane was being operated by Angel Flight Northeast, a group of volunteer pilots who help people who need to travel for medical treatment.

Amy Camerlin, a spokeswoman for the organization, said a cancer patient and his wife were being flown to Logan International Airport in Boston so the man could be treated at the nearby Dana-Farber Cancer Institute.

"Right now our primary concern is the family," Camerlin said. "Our thoughts and prayers go out to the family."

The other two recent crashes involved volunteers from Angel Flight organizations from other regions.

On July 17, a plane flown by an Angel Flight Southeast volunteer 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.

On June 3, a flight arranged by Angel Flight Central crashed in Iowa City, Iowa, killing a 2-year-old girl who had just been treated for clubfoot. Her mother and the pilot were injured.

The string of crashes was unprecedented for the charities, which have flown tens of thousands of patients to medical care over more than a decade.

The plane that crashed Tuesday was built in 1956 and took off from Westhampton Beach, N.Y., carrying the pilot and a Long Island couple, Peters said. He did not identify the victims.

Deputy Police Chief Allen Krajcik said he was in his cruiser Tuesday when he spotted the plane flying at a low altitude just before it dropped out of the sky.

"The plane just did a nosedive, straight down to the pavement," he said.

The plane's propeller was found about 50 yards from the crash site. Krajcik said it was uncertain whether it fell off or flew there on impact. Federal investigators were expected to arrive at the scene Wednesday.

The bodies were burned beyond recognition, and dental records may be needed to identify the victims, said Easton Fire Chief Thomas Stone.

The registered owner of the plane is Janet Keene of Brookfield, Conn., but she was not on board, according to her husband, Kenneth Keene.

Kenneth Keene said his wife inherited the plane and sometimes hired a pilot so they could use it recreationally, since neither of them could fly it. He said the plane was used by Angel Flight about once a month and he knew of no problems with the aircraft.

The plane crashed about 500 feet from the Hannaford entrance, near a road leading out of the lot. Firefighters and fire trucks surrounded the wreckage, where charred wings stuck out from the rest of the debris, which was covered in white cloth Tuesday afternoon.

Store manager Arthur Dechellis said the plane crashed in an area where people rarely park and no cars were hit.

Patricia Desgrosseilliers, manager of a bank near the crash site, said she heard a crash, then saw the plane burning.

"The flame was very tall, very high," she said. "There was a lot of smoke, thick black smoke. ... Everybody was pretty much horrified."

Click here for more on this story from MyFOXBoston.com.