GLENCOE, MINN. - Richard Gebhardt was heading across his farmyard to repair a tractor when he heard a roar and looked up into the low, drizzling clouds just after 11 a.m. Wednesday.

"At first I thought it was a jet; it was so low and so loud it almost made me want to duck," Gebhardt said. "Just that quick, it swooped right over and was gone."

The sound of a double explosion shook the muddy farm fields, and Gebhardt saw black smoke billowing across the road. He jumped in his pickup, called 911 on his cellphone and rushed to the scene.

But his hope of being able to help was quickly dashed when he found the bodies of three adults and three pet dogs thrown from the wreckage amid flames and smoke.

A relative identified the victims as 52-year-old pilot Stuart Dahlberg of Brooklyn Center; his mother, 76-year-old Mae Dahlberg of St. Cloud, and his wife, Ivelisse.

David Dahlberg said his brother was flying the three of them to Colorado to watch a high school play that his sister, a choral and drama director, was opening this weekend.

A classical pianist and longtime piano teacher, Mae Dahlberg rarely missed the performances of her daughter's students, David Dahlberg said.

Investigators from the Federal Aviation Administration combed through the crash site late into the night, hoping to figure out what went wrong.

"My brother is a careful guy when it comes to flying," David said, adding that Stuart Dahlberg owned the four-seat plane they were traveling in, a 1947 single-engine Beechcraft Bonanza.

David Dahlberg said his mother, an only child, earned a music education degree from Concordia College in Moorhead and married her husband, Francis Dahlberg, after graduation. She was a North Dakota farm wife for a big part of her life, cooking four meals a day for hired hands, keeping the house and teaching her children piano as part of their upbringing.

The family transitioned to an urban life when his father decided he wanted to work instead as a stockbroker specializing in commodity markets and moved them all to Minnetonka in the early 1970s, David Dahlberg said. Francis Dahlberg died in 2010.

Stuart Dahlberg, a computer programming consultant, was once an avid motorcycle rider, a master scuba diver, certified ski patrol member and flew airplanes for the past several years, his brother said. He had flown their mother to Colorado at least once before, he said.

David Dahlberg, who spoke on the phone from New Jersey, said his family is close, even though two of the four children live out of state. Another sister lives in Alexandria, Minn.

Mae Dahlberg was "difficult to rattle, never worried about much," he said. "My mom was my best friend after my wife."

Stuart Dahlberg was "idiosyncratic, a very bright guy, a stubborn guy," his brother said. It was ironic that his brother died in a plane crash, he said, after surviving a lot of near-misses in his life, including falling at a construction site as a boy and totaling motorcycles as an adult.

David Dahlberg said the family was in shock Wednesday night over what had happened.

The plane's wreckage was scattered over a 250-yard swath of black farm soil and crop stubble. Blue tarps covered the bodies until they were removed about 5 p.m.

"It sounded like 50 pileups at once -- it was a great big bang," said Matt Odenbrett, who was feeding calves on his farm about 3 miles away. He thinks he heard the plane's engine misfiring and wonders if the pilot was trying to land.

Gebhardt, 60, who has lived on his soybean and corn farm about 4 miles north of Glencoe his entire life, said the plane was traveling very fast. He said it was heading west when it came over his farm. But the scattered wreckage looked like it crashed while heading east, so he wonders if the pilot was trying to turn around.

A small grove of trees stands nearby, and Gebhardt thinks the plane was flying so low it might have clipped some branches with its wings.

"My initial reaction was that he was going too fast and too low," Gebhardt said. "This is awful, this is a total disaster and there was nothing in the world we could do."

Staff writer Paul Walsh contributed to this report. • 612-673-4767 • 612-673-7102