I Samuel - Chapter 31
The Death of King Saul
Meanwhile, Shaul and his army were fighting the Philistines. The Jews were overpowered; they retreated and were killed in large numbers. Shaul's sons Jonathan, Avinadav, and Malki-Shua were all killed in battle. (His son Ishboshes wasn't there, as we shall see in II Samuel.) Archers approached Shaul and he became scared of being captured, tortured, and an object of ridicule. Shaul asked his armor bearer to kill him before the enemy could take him, but the request was denied. Shaul then fell on his sword and died.
The people in the nearby cities who saw how handily the Israelite army had been defeated fled their homes, which were then occupied by the Philistines. The next day, the Philistine army went to plunder the corpses and they found Shaul. They severed his head from his body and displayed his remains and his armor as trophies.
The people of Yavesh-Gilad heard about this desecration. They went by night and captured the remains of Shaul and his sons from the Philistines. The bodies had started to putrefy, so they burned the flesh and gave the bones a proper burial.
The question of how Shaul could commit suicide is a complicated one, a full discussion of which is clearly beyond the scope of this synopsis. Suffice it to say that mitigating factors include the fact that Shaul knew that he was fated to die in this battle, and that his motivation was to avoid torture and a desecration of G-d's Name before an inevitable death.
To be continued in II Samuel...