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, supports training operations at the Pacific Missile Range Facility on Kauai Island, and is operated by Croman Companyan Oregon-based contractor, the Navy said.

The four people on the helicopter were all Croman employees, said Brian Beattie, director of operations at the company. The aircraft “performed routine training operations under contract with the US Navy,” he added.

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

Mr Beattie told Hawaii News Now that something was wrong when the helicopter tried to drop an object it had picked up from the water.

Witnesses described the helicopter suddenly descending.

Chris Turner, who owns a boat tour business, to Honolulu Star Advertisers that the helicopter was at the north end of the runway unloading luggage when it suddenly made an erratic right turn and then quickly crashed into the runway.

“It just went down,” said Mr. Turner to The Star-Advertiser. “That’s full speed. That’s crazy.”

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

The military conducted missile tests and training at the 2,385-acre base on the west coast of Kauai, Hawaii’s northernmost island. The naval base has more than 1,000 square miles of underwater range, for exercises involving submarines and surface ships, and 42,000 square miles of airspace.

Helicopter and plane crash deaths are not uncommon in Hawaii. In December 2019, seven people aboard a tourist helicopter died when the plane crashed on the southern side of Kauai. More than a dozen people died in another plane crash that year in Hawaii.

Tuesday’s crash on Kauai was one of several military-related helicopter crashes to have occurred on Tuesday morning. In Utah, two UH-60 Blackhawk helicopters crashed near Snowbird Resort during an exercise, Utah National Guard says. No injuries.