Complex sentence: Marcus is then struck in the shoulder by the meat cleaver, but manages to kick Martha toward the elevator shaft when the long necklace she's wearing gets caught in the bars of the shaft, and she's decapitated when he pushes the elevator button.
Split into simpler sentences: Marcus is then struck in the shoulder by the meat cleaver, but manages to kick Martha toward the elevator shaft. When the long necklace she's wearing gets caught in the bars of the shaft, she's decapitated when he pushes the elevator button.