A helicopter operated by a military contractor crashed during a training mission in Hawaii on Tuesday, killing all four people on board, the US Navy said.

The helicopter, a 58-foot-long Sikorsky S-61N, was supporting a training operation at the Pacific Missile Range Facility on the island of Kauai, and was operated by Croman Corporation, an Oregon-based contractor company. , the Navy said.

The four people aboard the helicopter were all Croman employees, said Brian Beattie, the company’s chief operating officer. The aircraft “was conducting routine training operations under contract with the United States Navy,” he added.

Late Wednesday, Mr Beattie identified those on board the helicopter as Daniel Maurice, 64, the chief pilot; Patrick Rader, 55, the command pilot; Ericka Tevez-Valdez, 42, mechanic; and Mathew Haider, 44, a mechanic.

Mr Beattie told Hawaii News Now something was wrong as the helicopter attempted to jettison an object it had retrieved from the water.

Witnesses described the helicopter suddenly descending straight ahead.

Chris Turner, owner of a boat tour company, told The Honolulu Star-Advertiser that the helicopter was at the north end of the runway lowering elements when it suddenly made a erratic right turn, then quickly nose-dived onto the track.

“It just fell,” Mr. Turner told The Star-Advertiser. “It was full speed ahead. It was crazy.”

The National Transportation Safety Board said in a social media post that the agency is investigating the accident.

The military conducts missile testing and training at the 2,385-acre base on the west coast of Kauai, the northernmost of the main Hawaiian islands. The naval base has over 1,000 square miles of underwater range, for exercises involving submarines and surface ships, and 42,000 square miles of airspace.

Helicopter and airplane crash deaths are not uncommon in Hawaii. In December 2019, seven people aboard a sightseeing helicopter died when the plane crashed on the south side of Kauai. More than a dozen people were killed in other plane crashes that year in Hawaii.

Tuesday’s crash in Kauai was one of several military-related helicopter crashes that occurred Tuesday morning. In Utah, two UH-60 Blackhawk helicopters crashed near the Snowbird Resort during a training exercise, the Utah National Guard said. There are no casualties.