2 Samuel 1:23-25 (KJV)
23 Saul and Jonathan were lovely and pleasant in their lives, and in their death they were not divided: they were swifter than eagles, they were stronger than lions.
24 Ye daughters of Israel, weep over Saul, who clothed you in scarlet, with other delights, who put on ornaments of gold upon your apparel.
25 How are the mighty fallen in the midst of the battle! O Jonathan, thou wast slain in thine high places.
2 Samuel 1
David Wept Over the Death Of Saul And Jonathan
When people we love die by the hand of someone else, this can cause anyone to act out in anger.