וַיַּכּ֤וּ הַיְּהוּדִים֙ בְּכׇל־אֹ֣יְבֵיהֶ֔ם מַכַּת־חֶ֥רֶב וְהֶ֖רֶג וְאַבְדָ֑ן וַיַּֽעֲשׂ֥וּ בְשֹׂנְאֵיהֶ֖ם כִּרְצוֹנָֽם׃
So the Jews struck at their enemies* with the sword, slaying and destroying; they wreaked their will upon their enemies.
*their enemies I.e., those armed forces that were reckless enough to attack despite the king’s declaration that the Jews could stand their ground with impunity; cf. v. 2 and 8.11.
(The above rendering and its footnote come from the RJPS translation, an adaptation of the NJPS translation.)
Who exactly is it whom the Jews kill in this chapter by the thousands (vv. 6, 15–16)?
According to the rules of engagement set forth in 8:11, only if the Jews are attacked by an armed force did they have permission to kill those aggressors, who had been forewarned that the lives of their families were also at risk.
In other words, some group(s) needed to be ridiculously single-minded enough to organize, load up with weaponry, and head over to the Jewish neighborhood—presumably with intent to exterminate and to plunder, even while knowing that the Jews were armed and ready. Only in that case were those Jews granted the right to fight back with impunity.
If nobody would attack the Jews, then nobody would get hurt. The decision to engage (or not) lay in the enemy’s hands. But at that point, as an old British adage puts it, “turnabout was fair play.”
In short, according to the plain sense of the biblical text, the Jews killed only those enemies who attacked, as stated in verse 2. The killing in this chapter was all done in self-defense.