“torture.” Saul was apparently afraid of being tortured, not of dying, because he asked his armor-bearer to kill him, and when the armor-bearer refused, Saul killed himself. How the Philistines would have tortured Saul since he was already badly wounded is not expressed but was clearly in the mind of Saul.
“Therefore Saul took the sword and fell on it.” This is how Saul died: he took his own life. The story told by the Amalekite was a lie (see commentary on 2 Sam. 1:6). The text reads “the sword,” not “his sword.” It is possible that Saul used the sword of the armor-bearer; perhaps he had dropped his in the battle. If so, then the armor-bearer used the same sword (1 Sam. 31:5).