According to the NYT
One of Mr. Roth’s remaining helicopters was a Bell 206 L-4, built in 2004 and owned by a firm in Louisiana. In September, that helicopter was found to have a mechanical problem in its main rotor gearbox, according to a service difficulty report filed with the Federal Aviation Administration. The report noted that bits of metal had been found in the oil of the helicopter’s transmission assembly, a possible sign of worn components.
It was this helicopter that [crashed] on Thursday