Complex sentence: When they open the door, Reece attempts to attack Darcy with a metal rod, and Darcy and his henchmen slam Pat's left hand in the door repeatedly and stab him with knives, breaking his fingers and mutilating his arm.
Split into simpler sentences: When they open the door, Reece unsuccessfully attacks Darcy with a metal rod. In response, Darcy and his henchmen slam Pat's left hand in the door and stab him repeatedly, breaking his fingers and mutilating his arm.