Complex sentence: Ed prepares a Molotov cocktail to fend them off, but Pete arrives and bites him, Shaun finally kills Pete before managing to get over the bar and using the cocktail to set fire to the bar, accidentally setting off the remaining rifle ammunition.
Split into simpler sentences: Ed prepares a Molotov cocktail to fend them off, but Pete arrives and bites him. He manages to get over the bar and Shaun uses the cocktail to set fire to the bar, accidentally setting off the remaining rifle ammunition.