Jeremiah 41:2

41:2 Ishmael son of Nethaniah and the ten men who were with him stood up, pulled out their swords, and killed Gedaliah, the son of Ahikam and grandson of Shaphan. Thus Ishmael killed the man that the king of Babylon had appointed to govern the country.

Jeremiah 41:6-7

41:6 Ishmael son of Nethaniah went out from Mizpah to meet them. He was pretending to cry as he walked along. When he met them, he said to them, “Come with me to meet Gedaliah son of Ahikam.” 41:7 But as soon as they were inside the city, Ishmael son of Nethaniah and the men who were with him slaughtered them and threw their bodies in a cistern.