Francisco said the damage to the skull in back is consistent with having been hit hard with a heavy object, apparently one of the three methods the Maya used to kill sacrificial victims (the other two being decapitation and splitting the rib cage to remove the heart). Francisco also said fourteen different sets of human remains have been identified in the cave, but those are on (or really partially in) the surface of the cave floor. He made the point that anything fully submerged in the rim pools is now surrounded by solid minerals and is almost impossible to find (the guide also said archeologists are experimenting with imaging technology to 'see through' the rock floor of the cave).
I made this photo by taking the shot just as Francisco shined his high power spotlight directly on the skull. The cave is an eerie place, and I think this photo captures some of that feeling.
(At one point in the cave when our group was waiting to climb to another level, Will starting singing the Indiana Jones theme music. This cave is a perfect Indiana Jones spot, and our group cracked up when they heard the tune.)