Seven Marines and four soldiers were presumed dead Wednesday after an Army Blackhawk helicopter crashed during a night training exercise at Eglin Air Force Base in the Florida Panhandle. Here’s an overview of what happened.

————

WHO WAS ON THE HELICOPTER

The Marines are part of a Camp Lejeune, North Carolina-based special operations group and the soldiers are from a Hammond, Louisiana-based National Guard unit, according to Eglin Air Force Base officials. The names of those involved have not been released, pending notification of their next of kin. A military official, who spoke to The Associated Press on condition of anonymity because the official wasn’t authorized to speak on the record, said they are presumed dead.

————

WEATHER CONDITIONS HAMPER SEARCH

Dense fog, a misty rain and darkness hampered search efforts for the UH-60 Black Hawk helicopter. The helicopter went down off of Navarre Beach on Santa Rosa Island, which is a barrier island in the Gulf of Mexico between Pensacola and Destin. The helicopter was on a routine night training mission when contact was lost. It had taken off from an airport in nearby Destin. The helicopter was reported missing about 8:30 p.m. CDT Tuesday.

————

THE BLACKHAWK HELICOPTER

The Black Hawk helicopter, developed by Sikorsky, has been used by the U.S. Army since 1978. It is known as a versatile, dependable and rugged helicopter. The Black Hawk joined other aircraft Tuesday night for a training mission. The cause of the crash is unclear.

————

THE CRASH SITE

Officials say the helicopter went down in a pristine and remote stretch of beach that has been under control of Eglin Air Force Base since before World War II. Only a small stretch of the beach is open to the public. The miles of glistening white sand beaches provide an important training and testing site for all branches of the military — from special forces who practice amphibious landings and invasion tactics to stealth fighter jets testing advanced weapons and guidance systems.

(AP)