One who was liable to the death penalty was killed, viz. "Then the elders of his city shall send, and they shall take him from there."
One who was not liable to the death penalty was let go, as it is written (Bamidbar 35:25) "then the congregation shall rescue the slayer."
One who was liable to exile would be returned to his place (in the city of refuge), viz. (Ibid.) "then the congregation shall return him to his city of refuge."
Rebbi says: The slayer himself would exile himself to the cities of refuge, thinking that they shielded the witting as well as the unwitting.