Refer to 35:19:4:1 and note. See also Oznayim la'Torah, who explains that it applies equally to Shogeg, in which case the Go'el ha'Dam may only kill him outside the Ir Miklat.
Rashi: Which explains why the Torah does not add the words "asher Yamus bah", as it does in connection with other objects
3)
Why does the Torah insert the (otherwise superfluous) words "Rotze'ach hu"?
1.
Sifri: To teach us that, if the murderer killed the victim by throwing pieces of metal at him he is Chayav - even though they are not Keilim.
4)
Bearing in mind that the victim may be a T'reifah, and killing him is not subject to Misah, how can Beis-Din sentence a murderer to death? How do they know that the victim is not a T'reifah?
1.
Chulin, 11b: This teaches us that we go after the majority - since the majority of people are not T'reifos.
1