וְשָׁלְחוּ זִקְנֵי עִירוֹ וְלָקְחוּ אֹתוֹ מִשָּׁם וְנָתְנוּ אֹתוֹ בְּיַד גֹּאֵל הַדָּם וָמֵת.
The elders of his city must take him [the intentional murderer] and hand him over to the blood avenger, and he shall die.
This is in the parsha of the unintentional murderer, where after specifying that a person guilty of culpable homicide is allowed to live in a city of refuge (or a Levite city), the Torah then deals with someone who intentionally killed another. Here the verse states that he is handed over to the blood avenger.
Is this literally so? My understanding is that if there are witnesses and a warning (עדים והתראה), then a murderer is sentenced to death, and the witnesses themselves are to be the executioners. Where exactly in halacha is a "blood avenger" given the right to execute a killer? Or is this one of the places where the Oral Torah overrides the simple understanding of the Written Torah?