Yes, you play the murderer, but also the people that have to solve the case. I'll try to make it more clear with an example. In the first scene you see your character murdering someone, and now there are several things you can do, hide the body, mob the floor, or just run like hell. A LOT can happen, if you bump into the waitress for example you will be doing a recreation of the face later in the game as the cop, it's all really interesting, and deliciously creepy.

(ps, in the US it's called Indigo project. which is odd, only the US uses Fahrenheit)