A helicopter crash killed four US Air Force crew members Tuesday night. Residents in the area of the accident claim they heard an unusual "misfiring" sound prior to the smashing of the helicopter against the marshland, the Telegraph reported January 8.

According to the report, the USAF Pave-Hawk was on a training mission on the north Norfolk coast when the chopper quickly plummeted into a marshland, killing all four on-board crew members.

The copter crashed at around 6 p.m. local time, according to the Air Force.

New York post reports that the chopper was actually based at the nearby Royal Air Force station in Lakenheath, Suffolk County, which hosts USAF units and personnel.

The aircraft was reportedly assigned to the 48th Fighter Wing and it was flying low prior to the incident.

Local police in Norfolk County said that the relatives of the crew members will be notified first before personal information and details of the victims can be released.

They added that ammunition was onboard the helicopter; hence the area were the crash happened was cordoned off to ensure the safety of the public.

Authorities said apart from the four crew members, no other person was put in any danger.

The cause of the accident is yet to be disclosed, and authorities said a full investigation could take months.

Pave Hawks is a modified version of Black Hawks. They typically fly low and fast at altitudes of hundreds instead of thousands of feet above the ground.

These choppers have been used for combat search and rescue operations. They have been deployed by the Air Force in several missions already, including the one in Japan in the wake of the 2011 tsunami and the other in 2005 when hurricane Katrina wreaked havoc in the country.