Amalek
In the second book of Samuel, a man told David that he is the son of an Amalekite and that he happened to be on Mount Gilboa after the battle. The man said that Saul asked him who he was and he told him “an Amalekite”. The Amalekite said that Saul asked him to kill him so that the Philistines couldn’t torture him and he killed Saul. David said the man was a murderer because he killed the King of Israel so David cut his head off.