To my eye, the Gaza photo appears to be illuminated by an off camera flash above and to the left of the camera. The man at the front on the left has a very bright left side of his face, and a very dark right side (also notice the shadow and light around his ear). Everything else in this photo seems consistent with this.

The reason for there appearing to be more dirt on the child's face is simply because it's a higher contrast image.

Maybe it has been manipulated more than is allowed, but I'm not seeing it.

EDIT: I'm not sure that there's only one artificial light source — notice how the front left man's visible ear is red? That's because it's being brightly illuminated from behind. Also notice that the top of his back (his left — photo right — shoulder) is illuminated, and that would be in shadow if the photo was only being lit by the flash that is lighting the left (his right) side of his face. Finally, there's another light source (maybe the sun?) that is causing the shine on the top right section of many of the heads (such as the bald man carrying the dead child).