We now find inserted in this long list of genealogy the scene of the death of Saul which we can also find in I Samuel 31:1-13. Feel free to read that for context. It is interesting that of all the events that take place in the life of Saul, he chooses the very last event of his life, which is when he takes his own life. I also find it interesting that we find a reason for why Aaul died in vs.13 and following. The reasons are the following: 1. He was unfaithful and 2. he consulted a medium.
The author goes on to say that "the Lord put him to death." It wasn't the Philistines, even though they were the invading army, but rather the hand of God which caused Saul to see a hopelessness which he felt required him to take his life. If you remember from I Samuel 11 Jabesh-gilead is where Paul is acclaimed king after he rescued this city from the Ammonites. Now they are putting his head on display as a trophy. We should never be surprised by history, it is fickle.