1)
Why does it say "Ka'asher Hogah"?
1.
Malbim: Once he was removed, even those who had been at the scene of the murder immediately went.
2)
What is the meaning of "Hogah"?
1.
Rashi: It was pulled. This is like "Hago Sigim mi'Kesef", "Hago Rasha Lifnei Melech" (Mishlei 25:4-5) (Radak - and "Hagah b'Rucho" (Yeshayah 27:8). The root is Hagah. The verse does not mention who did this.)
2.
Radak citing the grammarians R. Yehudah and R. Yonah: It is Hifil, from the root Yageh. This conjugation is like "Heglah" (Esther 2:6).