Complex sentence: Mahone immediately retrieves Tweener, takes him on a long ride, confesses to the murder of Oscar Shales, and murders Tweener execution style, and plants the gun to suggest that a struggle occurred.
Split into simpler sentences: Mahone immediately retrieves Tweener, takes him on a long ride, and confesses to the murder of Oscar Shales. He then murders Tweener execution style, and plants the gun to suggest that a struggle occurred.