The person that would kill such a creature would commit no sin. He, who slays him, slays one that has been already killed by his own acts. If killed, it is the dead that is killed.
तथागतं च यो हन्यान्नासौ पापेन लिप्यते॥ स्वकर्मणा हतं हन्ति हत एव स हन्यते।