It'd be very easy, actually, if it was the same camera, taking two shots one right after the other.
[Added later.]
What I wrote above, I wrote just before I read the linked article. I have to agree with the sense of credulity that such plagiarism accusations that turn out to be false are not more common. It seems that what happened here, must happen all the time—two people, on the same boat, bus, airliner, or other large conveyance, happen to see the same impressive sight, at about the same time, and end up taking nearly-identical pictures of it.