Complex sentence: After a confrontation Lenny and Mattie leave the bar and tells Louis that if he talks to Mattie again he will kill him after Louis says bye to Mattie Lenny shoots and kills Louis.
Split into simpler sentences: After a confrontation Lenny and Mattie leave the bar, and Lenny tells Louis that if he talks to Mattie again he will kill him. After Louis says bye to Mattie, Lenny shoots and kills Louis.