All nine service members on board have died after two U.S. Army Black Hawk helicopters crashed during a training mission in Trigg County, Kentucky, an Army official announced, calling it a "truly tragic loss."

The Black Hawk helicopters from the 101st Airborne Division -- one with five on board and another with four on board -- were on a "routine training mission" when they crashed at about 10 p.m. Wednesday, Army officials said. The helicopters were "flying a multi-ship formation under night vision goggles," officials said.

Brigadier General Lubas said the helicopters "have something very similar to the black boxes that we see on the larger aircraft, and we're hopeful that that will provide quite a bit of information on what occurred."

Trigg County, where the crash occurred, is about 25 miles northwest of Fort Campbell, a military installation on the Kentucky-Tennessee border.

Kentucky State Police troopers found the wreckage in a location described as either a field or a semi-wooded area, said Sarah Burgess, a police spokesperson.

Trigg County resident James Hughes saw the helicopters fly over his home then heard a loud boom, he told ABC News.

As his heart pounded, Hughes and a friend raced to the crash site where they saw two fires on the ground, he said.

"You could see parts of the helicopter," Hughes said.

"There wasn't anything anybody could do," he added.

The service members' names have not been released. Officials said they are in the process of notifying the families.

"We're gonna wrap our arms around these families and we're gonna be there with them," Kentucky Gov. Andy. Beshear said at a news conference Thursday.

Secretary of Defense Lloyd Austin said in a statement, "My heart goes out to the families of these service members and to the members of the 101st Airborne Division who bravely and proudly serve our country each and every day. I'm saddened by this tragic loss, and I am working with Army leadership to make sure our troops and their families receive the care that they need in the wake of this accident."

White House press secretary Karine Jean-Pierre said Thursday, "Our hearts and our prayers go out to their families during this very difficult time, as well as those who served alongside them at Fort Campbell."

"We will always honor our commitments to our service members and their families, and we stand with all who are grieving in the wake of this terrible, truly terrible accident," she said.