It's worth bringing this event into the discussion because it involves another Major who made the wrong decision at the time. Better the stuff come out early, if true, than that a low ranking military officer decide to cover it up.
I am sure you would never fail to report such things up the chain of command.
Well, like you said, "it is alleged", with regard to then-MAJ Colin Powell. With a stain like that, pretty amazing that is now Secy of State.
What I would do is irrelevant.