LEIPERS FORK, Tenn. — An airplane carrying a Louisiana plastic surgeon and two of his children who were scheduled to graduate from LSU on Friday broke up and went "violently out of control" before crashing in hilly terrain southwest of Nashville, investigators said Thursday.

Aaron McCarter, an air safety investigator with the National Transportation Safety Board, said at a news conference that a broad debris field and reports of the airplane's wings folding backward while in flight suggested a mid-flight catastrophe as the plane flew between Gonzales, La., and Louisville, Ky., on Wednesday.

The crash killed Dr. Lucius Doucet and his adult children Giselle and Jean-Luc Doucet. LSU issued a statement identifying the children and offered condolences.

"This is heartbreaking for the LSU community, but especially for those who know and love these two students, and those who were expecting to share graduation with them," the university statement said.

Flight logs show the plane left Gonzales and flew at 9,000 feet until reaching the Mississippi line, then settled in at 7,100 feet. It began flying erratically southwest of Nashville, losing speed and gaining altitude, according to data at Flightaware.com. The plane lost altitude and air traffic controllers lost contact with the plane when it was at an altitude of about 4,500 feet, McCarter said.

The damage field was about a mile wide, "indicating an in-air breakup," McCarter said. He asked nearby residents to review their security cameras for anything that could provide a clue. Investigators will consider human factors, the airplane itself and the weather. There was rain nearby around the time of the crash, he said.

About 15-20 people were gathering pieces of the aircraft and would lay them out at a hangar in Smithfield, Tennessee, he said. He estimated that about 75 percent of the airplane had been recovered by Thursday afternoon. Some parts may have fallen in a nearby lake, and a dive team from a neighboring county was called in to help.

The search team had recovered both stabilizers from the plane, along with both wings and much of the fuselage, McCarter said.

McCarter said that once he leaves the scene in one to two days, he would take about 10 days to prepare a preliminary report. A more complete summary will arrive in 9-10 months, then the NTSB would issue a report on a probable cause, if one can be established.

The aircraft, a Beechcraft BE35, was built in 1966. McCarter said it was not unusual for airplanes of that age to still be in service, given the detailed maintenance they undergo. "Their life span is a lot longer than an automobile."

The plane did not have a "black box" data recorder, but some instrumentation records might be on data cards inside the aircraft, he said.

Gonzales and Louisville are 628 miles apart. McCarter said the plane had plenty of fuel still left to cover the distance.

Doucet as an avid flight enthusiast and his pilot's license dates to at least 2017. He was certified to fly single-engine planes like the Beechcraft and was also rated for instruments, which are used in period of foul weather. Last year, he qualified for a "BasicMed" certification that doesn't require a full FAA medical certificate. He was required, while flying, to wear corrective lenses for both near and far vision

His practice, Williamson Cosmetic Center, issued a statement Thursday praising Doucet's passion for medicine and empathy for his patients.

"The sudden and untimely loss of Dr. Doucet has left a deep void in our hearts and in our practice. We understand that many of you had strong bonds with him over the years, relying on his expertise, guidance and unwavering support," the statement read.