HONOLULU (KHON2) — Former Black Hawk squadron Commander Ray L’Heureux said he is familiar with the Pacific Missile Range Facility, where four employees were conducting helicopter training and died in a crash on Tuesday.

“You can definitely see there’s a post crash fire — that the black smoke coming up from the mishap site, or the alleged mishap site, is unmistakable,” said Ray L’Heureux.

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L’Heureux said that the crash appeared to have happened near the runway.

“And when you hear the witnesses say they’re trying to recall how they saw the aircraft before it became not visible, it certainly then turned into what is visible is black smoke being sideways or not in control,” said L’Heureux. “You have to speculate that’s where the center of the investigation is going to begin.”

L’Heureux added that it’s not common for a helicopter to lose control in a runway environment and that, “it’s very rare unless something certainly went wrong mechanically.

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It is still unknown what caused the crash but the National Transportation Safety Board continues to investigate.