Detoro and many other directors and writers many times studied the animal world for inspiration so Allen's suggestion is really good. If you portraying a more human like killer I suggest watching the orginal Psycho, american psycho, house of 1000 corpses, and texas chainsaw massacre the orginal and even the remake as long as it has the former drill seargent in it. No matter what you are doing make sure you show intent in your eyes and actions even when wearing a mask alot of people will react to it because it will translate to how you move. Just don't go to far down the rabbit hole or you may have a hard time coming back >.<
If your wondering if you have intent if you can look at some one with no makeup on and with out saying a word but by just using your body face and eyes and convince them your about to remove their soul through their nostrils you got it.
If your a playing a victim if you can convince someone of your fear with out using your voice then you got it, because fear is like a plague and spreads swiftly even to those unsuspecting. after this you add in the vocals and you have a convincing performance that can help your patrons suspend their usual grasp on reality.