Complex sentence: Meanwhile, Jemm comes looking for Alex, who is ready with a gun and attacks him but he gains the upper hand and prepares to finish her off when a scaffold falls down in front of him and he's tackled by Hank.
Split into simpler sentences: Meanwhile, Jemm comes looking for Alex, who is ready with a gun and attacks him. However, he gains the upper hand and prepares to finish her off when he is suddenly attacked by Hank.