It would make your theory that Zelos and Youko were set up to fight one another after waking up much more plausible. The only reason I could think someone would do that is if they didn't want to get their hands dirty. But that wouldn't make sense if we were speaking of only one culprit, since the victims were rather gruesomely torn open.

The first culprite could have been detained or simply had no intention of returning to the school so that they could attempt to create an alibi for themselves.