Jamieson, Fausset and Brown on Jeremiah 41:9

9. because of Gedaliah--rather, "near Gedaliah," namely, those intercepted by Ishmael on their way from Samaria to Jerusalem and killed at Mizpah, where Gedaliah had lived. So 2Ch 17:15, "next"; Ne 3:2, Margin, literally, as here, "at his hand." "In the reign of Gedaliah" [Calvin]. However, English Version gives a good sense: Ishmael's reason for killing them was because of his supposing them to be connected with Gedaliah.