Complex sentence: Mortwell and Anderson then arrive to take back control of Simone and Cathy, and an enraged Simone shoots them both and then threatens to shoot George, but he punches her, takes the gun and leaves, upset at her ingratitude.
Split into simpler sentences: Mortwell and Anderson then arrive to take back control of Simone and Cathy, and an enraged Simone shoots them both dead and then threatens to shoot George. He punches her, takes the gun and leaves-upset at her ingratitude.