KERRVILLE, Texas (CBSDFW.COM/AP) – Three witnesses told investigators in Central Texas that they saw a small plane “spiraling” before it crashed into the ground belly down, killing all six people on board.

The Beechcraft BE58 crashed Monday morning as it approached Kerrville Municipal Airport, about 70 miles northwest of San Antonio.

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Beechcraft BE58 crash near Kerrville, Texas (CBS 11)

National Transportation Safety Board investigator Michael Folkerts says the twin-engine plane was last spotted on air traffic control equipment about 200 feet above the rocky terrain of Texas Hill Country.

Folkerts says it hit the ground “upright” about 6 miles from the airport in Kerrville, killing everyone aboard.

He says the plane crashed while moving at a high vertical but low horizontal speed that’s inconsistent with an attempted landing.

Construction worker Rodney Simmons said he heard a plane struggling.

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“I looked over and watched him drop down out of the clouds,” Simmons told the Express-News. “The rear end of the plane was real low, like he was trying to stay in the air. It was like he was dragging the tail end of that plane. Like he had a lot of weight in the back or something.”

The plane flew southward then “banked to the right, real hard, and just flipped on over, upside down, and nose-dived to the ground,” Simmons said.

The Texas Department of Public Safety says Jeffrey C. Weiss was piloting the plane. The plane’s co-owners say Weiss regularly volunteered to fly sick people from around the country to hospitals in Dallas and Houston.

DPS identified the passengers killed as: Houston landscape architect Marc Teppesen; his associate Mark Scioneaux; Houston architect Scott Reagan Miller; and Houston real estate investor Stuart Kensinger and his wife Angela Kensinger.

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(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)