ALBEMARLE COUNTY, Va. -- A man who said he saw a Virginia State Police helicopter crash outside Charlottesville said it sounded like the helicopter experienced a mechanical problem before it fell to the ground killing the two men inside.

Robby Noll was outside doing yard work Saturday when he said he looked up and saw the helicopter.

"It was very apparent that the pilot was trying to gain control of the craft," Noll said. "It appeared to honestly invert to turn upside down."

Noll said he watched helplessly as the Bell 407 helicopter dropped vertically tail down.

"It lost some parts, [they] seemed to fly off, and then it came down relatively quickly," he said. "Frankly I was a little shaken."

The Virginia State Police helicopter was flying over the Charlottesville-area assisting with public safety at the Charlottesville protests.

The troopers who were killed in the crash were identified as Lieutenant H. Jay Cullen, 48, from Midlothian, Va., and Trooper-Pilot Berke M.M. Bates from New Kent. Trooper Bates would have celebrated his 41st birthday on Sunday.

"We are deeply saddened by the loss of Jay and Berke, both of whom were our close friends and trusted members of our team. Jay has flown us across the commonwealth for more than three and a half years. Berke was devoted to our entire family as part of our Executive Protective Unit team for the past three years," Virginia Governor Terry McAuliffe said. "This is a devastating loss for their families, the Virginia State Police, and the entire commonwealth. Our hearts go out to their wives and children, and we stand by to support them during this difficult time. These heroes were a part of our family and we are simply heartbroken."

President Donald Trump also offered his condolences in a tweet to the "families and fellow officers of the Virginia state police who died today."

Deepest condolences to the families & fellow officers of the VA State Police who died today. You're all among the best this nation produces. — Donald J. Trump (@realDonaldTrump) August 12, 2017

Sources familiar with the operation said state police were filming the Charlottesville protests from the helicopter.

The helicopter crash is under investigation by the National Transportation Safety Board.

Virginia State Police indicated foul play was not suspected in the crash.

Interstate processional honors troopers killed in Charlottesville helicopter crash

An emotional scene played out along Interstate 64 Saturday night as the bodies of two Virginia State Police troopers who died in a helicopter crash in Charlottesville were transported home to Richmond.

Law enforcement, firefighters and other observers gathered on overpasses along the interstate to honor the troopers.

As the processional neared, state troopers temporarily blocked the interstate's on ramps, as is procedure to keep traffic back from the official escort.

Lt. Cullen graduated from the Virginia State Police Academy in May 1994 as a member of the 90th Basic Session. He first joined the Virginia State Police Aviation Unit in 1999.

Cullen is survived by his wife and two sons.

Trooper-Pilot Bates graduated from the Virginia State Police Academy in August 2004 as a member of the 107th Basic Session. He had just transferred to the Aviation Unit as a Trooper-Pilot in July.

Bates is survived by his wife, a son, and a daughter.