KERRVILLE — A man regularly volunteered to fly sick people in remote parts of the country to hospitals in Houston and Dallas was at the controls of a twin-engine airplane that crashed Monday in the Hill Country of central Texas, killing all six aboard.

Jeffrey C. Weiss, 65, was a senior vice president for investments at Raymond James and Associates in Houston. The Texas Department of Public Safety said Weiss, who co-owned the Beechcraft BE58, was at the controls when the aircraft went down just before 9 a.m. Monday while approaching Kerrville Municipal Airport, about 70 miles (110 kilometers) northwest of San Antonio.

Also killed were Stuart Roben Kensinger, 55; Angela Webb Kensinger, 54; Mark Damien Scioneaux, 58; Scott Reagan Miller, 55; and Marc Tellepsen, 45, all of Houston, said DPS Sgt. Orlando Moreno.

The aircraft went down just before 9 a.m. as it approached an airport in Kerrville, a city about 70 miles (110 kilometers) northwest of San Antonio, according to Federal Aviation Administration spokesman Lynn Lunsford. State law enforcement officials secured the crash site ahead of FAA and National Transportation Safety Board investigators’ arrival Monday.

The aircraft had taken from an airport outside Houston earlier Monday and crashed about 6 miles (10 kilometers) northwest of Kerrville Municipal Airport, Lunsford said. The flight was not a scheduled commercial route, he said.

The downed plane was manufactured by Raytheon Aircraft in 1999 and was co-owned by Weiss and Charles Morina of Dallas, according to FAA records.

Weiss loved to fly and the pair volunteered their time transporting sick people from remote regions to Texas hospitals for Angel Flight, Morina said.

“We flew people from all over the country to Dallas and Houston” for medical treatment, he told The Associated Press.

The cause of the crash hasn’t been determined. However, witnesses heard the plane struggling and sputtering moments before it crashed.

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

Construction worker Rodney Simmons said he heard a plane “struggle against the wind.”

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

The family of one of the six people killed in the crash of a twin-engine aircraft in the Texas Hill Country said the purpose of the flight was to survey some property.

In a statement to KTRK-TV of Houston, the family of Houston landscape architect Marc Teppesen said he and associate Mark Scioneaux were on the scouting trip when Houston architect Scott Reagan Miller, Houston real estate investor Stuart Kensinger and his wife Angela Kensinger, and Houston investment banker Jeffrey Weiss died in the Monday plane crash.

Weiss was a philanthropist who not only flew the sick to hospitals but was active in charities supporting children with special needs or who suffered abuse, said friend Bob Fuller. He told KPRC-TV of Houston that Weiss helped him conduct his Keels and Wheels charity event in Seabrook each year to aid abused children, giving both his time and money.

“I loved the man, I’ll tell you that. He was generous to a fault. He wanted to support our charity any way he can and one of those was if I wanted to fly to Detroit to talk to General Motors, ‘Call me first,'” Fuller said.

This story has been updated.