What does Jeremiah 40:16 mean?

Ishmael and the ten men with him got up and attacked Gedaliah son of Ahikam, killing him with the sword. Ishmael murdered the man the king of Babylon had appointed governor over the land. Jeremiah 40:16 - Modern Text Bible

(Ishmael betrays Gedaliah, killing him and overturning the fragile peace.)