Story related and cannot be missed.
In Case 7 - Solomon, you will come to a point where you open a door and Zeke the Slicer, will attack you. Note that this is actually the second time he attacks. After a quick sprint through the hallways, stopping only to grab the puzzle piece from the stairwell, you will shove a bookcase in front of a doorway and block him. Exit this room to the very next room. Hit the lever on the floor and mash the button to get the spike panels to turn. When Zeke comes running through the door in between the panels, they will crush him and you'll be 15 richer.