The Fall of Saul
V1-12 is a exact copy of the last chapter of 1 Samuel, chapter 31.
v13-14 are unique to 1 Chronicles, these two verses are not in 1 Samuel. It provides us a clear reason of the fall of Saul: because he was unfaithful to the LORD; he did not keep the word of the LORD and even consulted a medium for guidance, and did not inquire of the LORD.
It was God will put Saul to death. God was not cruel, He has given Saul 40 years of opportunity as King of Israel, however Saul did not show any sign of repentance of his unfaithfulness to God.
Faithfulness is what is the Lord Jesus seeking in His church (Matt 25), are you faithful to the calling of the Lord in your life?