Herod commanded soldiers to execute the guards.

Acts 12:18-19

18 The next morning the soldiers who had been guarding Peter became terribly distressed, because they did not know what had happened to him. 19 Then Herod heard about it. So he commanded soldiers to search for Peter, but they did not find him. Then he questioned the soldiers who had been guarding Peter, and asked them, “How did Peter get away when you were there guarding him?” But they could not explain it. So he commanded them to be led away to be executed {other soldiers to lead them away to execute them}. Afterwards, Herod went from Judea province down to Caesarea, where he stayed for some time.