MANCHESTER, Ky. — A medical helicopter crashed in eastern Kentucky, killing all three crewmembers aboard.

A statement from Air Evac Lifeteam said the accident happened in Clay County at 11:16 p.m. Thursday.

There was no patient on board. The helicopter came down in an elementary school parking lot in what witnesses described as a dense fog.

Ed Ray, a meteorologist at the National Weather Service’s Jackson, Ky., office said he didn’t have any information about fog in the area but said there was no violent weather overnight in the area of the crash.

The company identified the crew members as pilot Eddie Sizemore, flight paramedic Herman “Lee” Dobbs and flight nurse Jesse Jones. They were on their back to base in Manchester, Ky., after taking a patient to a hospital in London, Ky.

Air Evac Lifeteam President and CEO Seth Myers said the company is devastated by the loss of the crew.

The cause of the accident will be investigated by federal air safety officials.