I would say the X set of foot prints are ernies because the mop suggests he was mopping the floor and ran away threw the water when the shooter came it, but i also think the killer was Check C because they appear to be left handed and if they leaned against the wall with their right hand they would have shot with their left hand which would make that their dominate hand
Short/simple answer: because it was forbidden to picture or sculpt anything figurative (i.e. representing a being or object). Figurative art could be wrongly interpreted as a depiction of Allah and worshipped instead of Him, and that would be considered idolatry.
