Melgar, a staff sergeant in the Army’s 3rd Special Forces Group, was specifically selected for an intelligence operation in the West African nation of Mali. He was well respected by the American Embassy staff and the partner forces there, a former U.S. Africa Command official said. But shortly before he died, Melgar told his wife that he had a bad feeling about two of his partners in that effort, both of whom were members of SEAL Team Six.

Not wanting to say much more, Melgar informed his wife, Michelle, that he’d tell her the full story when he got back home, according to an official speaking on condition of anonymity because the investigation is still ongoing.

Now those two Navy SEALs are under investigation for killing Melgar—an investigation, first reported by The New York Times, sending shockwaves throughout the special-operations community. Military experts were hard-pressed to think of another case where elite U.S. troops turned on one another.