The Philistines battle the Israelites on Mount Gilboa. All of Saul's sons are killed, including Jonathan (1-2).
While Saul is fighting, he's injured badly by Philistine archers.
Afraid that the Philistines will find him and abuse his body, Saul begs his armor boy to run him through with his sword. At this time, this was considered an honorable death. Not so much anymore.
The boy is too afraid to take Saul's life, so Saul stabs himself with his own blade and falls down dead. When Saul's armor-bearer sees this, he collapses on his own sword and dies (3-6).
The Philistines find Saul's body on Mt. Gilboa. They cut off his head and strip him of his armor. They spread the good news to their temples, and then put Saul's armor in the temple of the goddess Astarte. They fasten his body to the wall of Beth-shan (8-10).
Some Israelites travel all night long to recover the bodies of Saul and his sons from the wall of Beth-shan. They bury their bodies under a tree and refuse to eat anything for seven days.
In spite of all of the triumphs of Israel in I Samuel, the book ends on the sad note of Saul's death (11-13).