Some translations set poetry farther to the right than the rest of the text to show that it is poetry. The ULB does this with the poetic song in 3:33-34.
David never wanted to hurt Saul's family. Isbosheth criticized Abner and Abner became angry. He decided to help David become king of all of Israel. Abner came and made a treaty with David. As he left, Joab arrived and told him he wanted to talk to him and he murdered Abner. David was very unhappy that Abner had been killed.