“happened, yes, happened.” The Amalekite uses the figure of speech polyptoton to emphasize that it was only mere chance that he was on the slopes of Mount Gilboa and came upon the wounded Saul. The Amalekite apparently hoped that would make his story more believable, since he had not been a part of Saul’s bodyguard.
[For more on the figure polyptoton and the translation of the figure, see commentary on Gen. 2:16, “eat, yes, eat.”]
This Amalekite made up a story about mercifully fulfilling Saul’s request and killing him quickly rather than letting the Philistines come upon him while he was still living, which might even lead to Saul’s being tortured. He apparently hoped to win David’s favor and likely wealth and fame along with it. But David had the Amalekite executed. The exact reason is not given. It is possible that David was not fooled by the man’s lie especially if the Amalekite, thinking that Saul was David’s enemy, showed signs of glee or satisfaction along the lines of, “I killed your enemy.” It is also possible that David thought if Saul could communicate so clearly then the Amalekite should have tried to rescue him. It is also possible that because the person was an Amalekite he was immediately suspected of treachery and David sought for more information. In that case, even though the text does not say so, it is possible that David started hearing from others who came from the battle (not every Israelite was dead). In any case, the Amalekite said he killed Saul, Yahweh’s anointed, and was executed for it. 1 Samuel 31:3-5 tells us what actually happened, and this Amalekite was snared by his own words (Prov. 6:2).