I would chime in in agreement with most folks here - I don't think you could get a single attorney to take this to court if you wanted to claim infringement. There are enough details about the image that are different (model A is nude, hidden in soap bubbles, in a tub, in black-and-white. Model B is more svelte, wearing a corset, in a shower stall, using a fake gun, shot at a different angle, in color, with different lighting). While it may show a lack of original thinking on the other photographers' part, it doesn't rise (or descend, as your thought may incline) to the level of copyright infringement. As has been noted here also, you can't copyright a concept, like "naked woman with gun".
There was a case a few years ago where a photographer shot a sunset through the open legs of a bikini-clad model. Some ad agency saw the image, then hired another photographer to basically duplicate the shot for a client when the original photographer declined to license the image at a price the client was willing to pay. About the only thing that was different between the two was the tint of the sunset - the one was more orange/red, the other more brown. The pose was identical, the lighting, identical. You could even recognize certain elements of the lanscape in the shot that showed they were photographed in essentially the same geographic location.
THAT is the level of proof you'd have to demonstrate to claim copyright violation.
Since the other photographers' image has been posted here without his consent, if he were to discover it, he could sue for usage, but not for copyright violation. Nowhere is the ownership of the image being claimed to be that of anyone but the original photographer. He'd also have a hard time getting any kind of punitive damage, since there is clearly no demonstrable profit being made from the use. Worst case scenario, the image link would have to be removed.
To offer a properly grounded critique of the image(s), I find both of them disturbing and distasteful because of the association of sex and violence. In both cases, the models appear to be responding violently to an intrusion into their private space. These feel like watching some kind of S/M rape fantasy.
There's an interesting Freudian duel going on between the phallus of the gun and the phallus of the camera. In both cases, it appears that the phallus of the camera, the power of the voyeur, trumps the power of the gun. The voyeur's violation of private space succeeds, in spite of, or perhaps because of, the threat of violence from the gun. That is, the women can only have unfulfilled potential, whereas the viewer has unlimited opportunity to satiate the desire to violently intrude upon the women.