This is a polite way of saying "killed them." It might be best to translate so that the reader understands that other people might have helped the king do this. (See: [[rc://en/ta/man/translate/figs-euphemism]] and [[rc://en/ta/man/translate/figs-explicit]])
Judah, the name of the people group, is a metonym for the people themselves. AT: "the people of Judah went out of their land" (See: [[rc://en/ta/man/translate/figs-metonymy]])