When they are in the building finding all the killer's research including Lou's college thesis, you can see the 3 masked mannequins behind Detective Russo. In this shot they all have solid eyes. When Patrick comes in, the killer runs out from being the middle mannequin and puts the blade to Lou's neck. At this point he still has solid eyes. They show the killer's mask one last time before Patrick puts his gun down and at that time the killer's mask has the eyes cut out.
When the lady is helping an injured senior, she wraps his head and then lifts up his shirt to check another injury and when her partner starts asking a question they cut back to her and she is just starting to wrap his head.