1)
Having discussed where the murderer killed the victim with metal, stone or wood, what is this Pasuk referring to?
1.
R. Bachye and Sifri: It is referring to where he killed him by deliberately pushing him off a roof 1 (or by throwing pegs or beams of wood at him or rolling (large) stones on to him - Targum Yonasan).
1
R. Bachye: In which case one needs to assess that it was from a height of at least ten Tefachim - in which case it is lethal. See also Torah Temimah, note 33.
2)
What does "bi'Tzediyah" mean?
1.
Rashi and Targum Onkelos: It means that he lay in wait for him (and actually meant to kill him).
2.
Targum Yonasan: It means that he killed him deliberately (be?Meizid).
