(Devarim, Ibid. 12) "and they shall place him into the hand of the avenger of blood and he shall die": Whence is it derived that if he did not die at the hands of the avenger of blood, he is to die at the hand of any man? From "and he shall die."
(Ibid. 13) "Let your eye not pity him, and remove the innocent blood from Israel": Lest you say: If one has already been killed, why should we be guilty of the blood of others? It is, therefore, written "Let your eye not pity him."
"and remove the innocent blood": Remove the doers of evil from Israel.