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DAKOTA CITY, Iowa — A small, experimental helicopter went down in Humboldt County last night killing one person on board and critically injuring the other. The gyro-copter crashed in the 2000 block of K Rd north of Dakota City around 7 p.m.

The pilot, 58-year-old Larry Erickson, died at the hospital. His passenger, 65-year-old Mike Chapman, was airlifted to Des Moines for “serious” injuries.

Witnesses say it sounded like the helicopter was about to land right before it came crashing down in Chapman’s front yard.

“All of a sudden, heard the engine rev up big time. Right then is when it hit the tree,” said neighbor Spud Colwell.

Colwell and his wife were watching the two-seat helicopter fly over the area from their front porch. He dashed across the street and called 911.

“Mike was lying on the ground and Larry was still wearing his harness,” said Colwell.

Humboldt County Sheriff Dean Kruger says the pair was taking pictures of Chapman’s acreage. It`s unclear what caused the gyro-copter to suddenly lose altitude and plummet to the ground.

“Just a sad thing that happened. I know Mr. Erickson, he flew that thing all the time,” said Kruger.

Investigators from the FAA and NTSB spent the day in Humboldt County trying to determine what caused the deadly crash.

“If there was any engine failure, anything unusual for this to have happened,” said Kruger.