On September 1, 2017, at 1058 eastern daylight time, a MD Helicopters 369FF, N5189K, was substantially damaged while maneuvering to land at Gwinnett County Airport (LZU), Lawrenceville, Georgia. The commercial pilot and a pilot-rated crewmember were seriously injured. The helicopter was operated by the Gwinnett County Police Department as a local, public-use flight. Day, visual meteorological conditions prevailed at the time, and no flight plan was filed. The flight originated at LZU about 1000. The pilot reported the following that the preflight inspection of the helicopter and en route portions of the flight were uneventful. After about 1 hour on station performing law enforcement duties, the pilot returned to LZU to get ahead of deteriorating weather conditions. The flight was cleared to land on taxiway whiskey, then perform a side-step maneuver to the police helipad. The pilot recalled winds from 220° at 10 knots. He performed a normal approach to a 10-foot hover to taxiway whiskey. As he made a left turn to line up with the helipad, he noted that the cart on the helipad was not set up for a landing into the wind. He elected to discontinue the approach and make a right turn to land on a wash rack, into the wind. As the pilot was about to initiate the turn to the wash rack, the pilot noted a "strong wind gust" followed by a "sudden, uncommanded, violent, right yaw" and "what seemed to be an uncommanded climb." He applied cyclic and pedal inputs; however, the helicopter continued in a right spin for at least two full rotations until it impacted the ground. The pilot and crewmember were met by first responders and transported to a local hospital for treatment of their injuries. The pilot later reported that a small, county-owned outbuilding near the police pad can mask or block the wind, creating a turbulent effect. He stated that the perceived wind gust could also have been the tail rotor becoming "unmasked" from behind the outbuilding. The pilot further reported there were no preimpact mechanical malfunctions or anomalies that would have precluded normal operation of the helicopter. An inspector with the Federal Aviation Administration responded to the accident site and examined the wreckage. He reported that the helicopter came to rest on its right side in the grass, adjacent to a taxiway. There was no fire. Structural damage to the fuselage, tail rotor, and main rotor were confirmed. The main rotor blades were severed during the impact and were scattered up to 220 feet from the main wreckage. His examination of the wreckage did not reveal evidence of a mechanical malfunction or anomaly.