At approximately 7:20 p.m. Sept. 21, the drone, or unmanned aerial vehicle, and the helicopter collided. The Army helicopter sustained damage to its main rotor blade, window frame and transmission deck. A motor and arm from a small drone, identified as a DJI Phantom 4, were recovered from the helicopter. The NTSB was notified of the incident Sept. 22 and began its investigation that day. In the following days investigators were able to identify and subsequently interview the drone operator. The drone operator also provided flight data logs for the incident flight.