Authorities investigate at the crash scene of a twin-engine Beechcraft BE58, Monday, April 22, 2019, near Kerrville, Texas. The pilot and the five other people aboard the plane were all killed, said Sgt. Orlando Moreno, a spokesman for the Texas Department of Public Safety. (William Luther/The San Antonio Express-News via AP)

KERRVILLE, Texas (AP) — Witnesses saw a small plane "spiraling" over the rocky terrain of Texas Hill Country before it crashed into the ground, landing on its belly and killing the pilot and five passengers on impact, a federal official said Tuesday.

People around the crash site described hearing the twin-engine plane sputter Monday morning, and a National Transportation Safety Board investigator said when air traffic control last spotted the Beechcraft BE58 it was about 200 feet (80 meters) above the ground and more than 6 miles (10 kilometers) from its intended runway.

The plane slammed to earth northwest of Kerrville about 70 miles (110 kilometers) northwest of San Antonio at a high vertical but low horizontal speed inconsistent with a landing attempt, NTSB investigator Michael Folkerts said during a Tuesday press conference. He said all six on board were killed "on impact."

Jeffrey C. Weiss was piloting the aircraft when it went down as it approached Kerrville Municipal Airport, according to the Texas Department of Public Safety. Folkerts described Weiss, a 65-year-old investment manager, as an experienced pilot, and friends said he often volunteered to fly sick people to Texas hospitals.

Federal Aviation Administration and NTSB investigators will continue to study the crash site for a few more days and intend to review engine data and examine the plane's propellers before issuing preliminary findings as soon as next week, Folkerts said.

The family of Houston landscape architect Marc Teppesen, 45, told KTRK-TV that they believe an architectural client had chartered the doomed plane to survey some property. Teppesen was killed alongside his 58-year-old associate Mark Scioneaux, 55-year-old architect Scott Reagan Miller, 55-year-old Houston real estate investor Stuart Kensinger and his 54-year-old wife Angela Kensinger, officials said.

Folkerts said the group was traveling to the area for "business dealings."

Witnesses described the plane's last moments.

"It was making a sput-sput sputtering sound, like the engines were cutting out," Treva Hardeman told the San Antonio Express-News . She said she was working at home about a quarter of a mile from where the aircraft crashed. "It was just a few seconds later that I heard the boom."

Construction worker Rodney Simmons said he heard a plane struggling.

"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.

Kerr County Sheriff Rusty Hierholzer, center, makes a phone call, Monday, April 22, 2019, where his deputies guard the entrance to a private road near Kerrville, Texas, where a twin-engine Beechcraft airplane crashed earlier in the day, killing all six people on board. (Bob Owen/The San Antonio Express-News via AP)