Who killed Saul?
1 Sam 31:4 Saul was cornered by the Philistine army and didn’t want to be killed by them so he told his armor bearer to do it. But the armor bearer refused to kill his own king so Saul took out his own sword and fell on it. He killed himself. As for the passage in 2 Sam. 1:15… That is referring to the Amalekite who came to David saying that he had murdered King Saul and David had him killed for killing the Lord’s anointed. The Amalekite obviously lied to try to save himself from David who he thought would be excited at Saul’s death since Saul was trying to kill David. So in answer to your question… Saul killed himself.