Complex sentence: Costello thanks her, makes his way to the square and begins to shoot a great many of the guards as well as Fung as chaos ensues, however, Fung turns out to be wearing a bulletproof vest.
Split into simpler sentences: Costello thanks her, makes his way to the square and begins to shoot a great many of the guards as well as Fung as chaos ensues. However, Fung turns out to be wearing a bulletproof vest.