unfortunately, it doesn't make much sense saying that in French, as being "l'assassin de" is usually followed by a person's name or an "object" (gramatically) that was supposed to be living before being murdered(thus dead after being murdered). One doesn't say "je suis l'assassin d'un crime" we say "je suis l'assassin" d'une personne -ou d'un être vivant-.
This is why J4MES is right when he translates : "je suis l'assassin dans mon propre crime" (note that "meurtre" would be better here...)