II Kings 14:5 Midrash

וַיְהִ֕י כַּאֲשֶׁ֛ר חָזְקָ֥ה הַמַּמְלָכָ֖ה בְּיָד֑וֹ וַיַּךְ֙ אֶת־עֲבָדָ֔יו הַמַּכִּ֖ים אֶת־הַמֶּ֥לֶךְ אָבִֽיו׃

And it came to pass, as soon as the kingdom was established in his hand, that he slew his servants who had slain the king his father;