Story related and cannot be missed.
In Case 8 - Michael, you will come to a room with shipping boxes and another Rammer with hedgehog spikes in his chest. The first time you fought him you had to get him stuck in the wooden boxes and hit him with weapons. This time, if you run around you will find a crane control with a wooden box near it. Dodge and get him stuck in the wood, grab the crane control, which already has a box on it, position it over him and drop it on his spiky head. After he dies be sure to lift the box again and search his body for the key you need.