Find a random person. Kill them in a Brutal fashion, similar to how the killer is killing people, and hide the body to be found later. Help the rest of the group work on there plan to take down the killer. There is no way that a copycat killer is going to just be randomly murdered during the course of the movie, or revealed before the twist ending. I won't be killed, my crime needs to be discovered while I'm still alive to build up tension. Inevitably, the killer would be stopped, everyone would be relieved, and then some hint, either to the characters or the audience, will let everyone know that I am the premise for a sequel. If it is just me and one other survivor, and the killer has been eliminated, then make sure that I am always standing behind the last person with a weapon. If they have a sudden look of shocked realization, always be ready to hit them with the weapon, and walk away dramatically. Then, I just never kill again. No sequel, I'm safe.