Tarrian
If the crucified fellow can be saved:
Tarrian gets someone with some restorative Materia to heal the scavenger as he has Cenereo release him. When he's up to talking he asks who/what did this and why.
If he's too far gone:
Passing by the crucified scavengers, Tarrian asks for a volunteer to join him on Cenereo for an aerial assessment of the power plant before going in, preferably someone with decent who'll actually be able to see what's going on (Tarrian's Awareness is terrible).